From 557c364cc7a01f2c9ba0d17d16fee279eb0dcf89 Mon Sep 17 00:00:00 2001
From: stkao05 <st.kao.05@gmail.com>
Date: Thu, 2 Mar 2017 01:58:36 +0800
Subject: [PATCH 01/10] Try re-establish IDBDatabase connection after encoutner
 InvalidStateError error

---
 src/drivers/indexeddb.js | 110 ++++++++++++++++++++++++++++++---------
 1 file changed, 84 insertions(+), 26 deletions(-)

diff --git a/src/drivers/indexeddb.js b/src/drivers/indexeddb.js
index 51f936d..b27d276 100644
--- a/src/drivers/indexeddb.js
+++ b/src/drivers/indexeddb.js
@@ -115,6 +115,19 @@ function _advanceReadiness(dbInfo) {
     }
 }
 
+function _rejectReadiness(dbInfo, err) {
+    var dbContext = dbContexts[dbInfo.name];
+
+    // Dequeue a deferred operation.
+    var deferredOperation = dbContext.deferredOperations.pop();
+
+    // Reject its promise (which is part of the database readiness
+    // chain of promises).
+    if (deferredOperation) {
+        deferredOperation.reject(err);
+    }
+}
+
 function _getConnection(dbInfo, upgradeNeeded) {
     return new Promise(function(resolve, reject) {
 
@@ -262,6 +275,47 @@ function _fullyReady(callback) {
     return promise;
 }
 
+// Try to establish a new db connection to replace the
+// current one which is broken (i.e. experiencing
+// InvalidStateError while creating a transaction).
+function _tryReconnect(dbInfo) {
+    _deferReadiness(dbInfo);
+
+    var dbContext = dbContexts[dbInfo.name];
+    var forages = dbContext.forages;
+
+    for (var i = 0; i < forages.length; i++) {
+        forages[i]._dbInfo.db.close();
+        forages[i]._dbInfo.db = null;
+    }
+
+    return _getConnection(dbInfo, false).then(function(db) {
+        for (var j = 0; j < forages.length; j++) {
+            forages[j]._dbInfo.db = db;
+        }
+    }).catch(function(err) {
+        _rejectReadiness(dbInfo, err);
+        throw err;
+    });
+}
+
+function createTransaction(dbInfo, mode) {
+    try {
+        var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
+        return Promise.resolve(tx);
+    } catch (err) {
+        if (err.name === 'InvalidStateError') {
+            return _tryReconnect(dbInfo).then(function() {
+
+                var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
+                return Promise.resolve(tx);
+            });
+        }
+
+        return Promise.reject(err);
+    }
+}
+
 // Open the IndexedDB database (automatically creates one if one didn't
 // previously exist), using any options set in the config.
 function _initStorage(options) {
@@ -355,6 +409,7 @@ function _initStorage(options) {
     });
 }
 
+
 function getItem(key, callback) {
     var self = this;
 
@@ -367,9 +422,9 @@ function getItem(key, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly')
-                .objectStore(dbInfo.storeName);
+            return createTransaction(self._dbInfo, 'readonly');
+        }).then(function(transaction) {
+            var store = transaction.objectStore(self._dbInfo.storeName);
             var req = store.get(key);
 
             req.onsuccess = function() {
@@ -399,10 +454,9 @@ function iterate(iterator, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly')
-                .objectStore(dbInfo.storeName);
-
+            return createTransaction(self._dbInfo, 'readonly');
+        }).then(function(transaction) {
+            var store = transaction.objectStore(self._dbInfo.storeName);
             var req = store.openCursor();
             var iterationNumber = 1;
 
@@ -462,8 +516,13 @@ function setItem(key, value, callback) {
             }
             return value;
         }).then(function(value) {
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
+            return createTransaction(self._dbInfo, 'readwrite').then(function(transaction) {
+                return [transaction, value];
+            });
+        }).then(function(txAndValue) {
+            var transaction = txAndValue[0];
+            var value = txAndValue[1];
+            var store = transaction.objectStore(self._dbInfo.storeName);
             var req = store.put(value, key);
 
             // The reason we don't _save_ null is because IE 10 does
@@ -510,9 +569,9 @@ function removeItem(key, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            var dbInfo = self._dbInfo;
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
+            return createTransaction(self._dbInfo, 'readwrite');
+        }).then(function(transaction) {
+            var store = transaction.objectStore(self._dbInfo.storeName);
 
             // We use a Grunt task to make this safe for IE and some
             // versions of Android (including those used by Cordova).
@@ -546,9 +605,9 @@ function clear(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            var dbInfo = self._dbInfo;
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
+            return createTransaction(self._dbInfo, 'readwrite');
+        }).then(function(transaction) {
+            var store = transaction.objectStore(self._dbInfo.storeName);
             var req = store.clear();
 
             transaction.oncomplete = function() {
@@ -571,9 +630,9 @@ function length(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly')
-                .objectStore(dbInfo.storeName);
+            return createTransaction(self._dbInfo, 'readonly');
+        }).then(function(transaction) {
+            var store = transaction.objectStore(self._dbInfo.storeName);
             var req = store.count();
 
             req.onsuccess = function() {
@@ -601,12 +660,12 @@ function key(n, callback) {
         }
 
         self.ready().then(function() {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly')
-                .objectStore(dbInfo.storeName);
-
+            return createTransaction(self._dbInfo, 'readonly');
+        }).then(function(transaction) {
+            var store = transaction.objectStore(self._dbInfo.storeName);
             var advanced = false;
             var req = store.openCursor();
+
             req.onsuccess = function() {
                 var cursor = req.result;
                 if (!cursor) {
@@ -648,10 +707,9 @@ function keys(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly')
-                .objectStore(dbInfo.storeName);
-
+            return createTransaction(self._dbInfo, 'readonly');
+        }).then(function(transaction) {
+            var store = transaction.objectStore(self._dbInfo.storeName);
             var req = store.openCursor();
             var keys = [];
 

From bcf62c531a52b2858c3938f98e7d2706e20fbdff Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sat, 6 May 2017 23:49:35 +0300
Subject: [PATCH 02/10] test(api): test IDBD reconnect after InvalidStateError

---
 examples/indexeddb-invalidstate.html | 38 ++++++++++++++++++++++++++++
 test/test.api.js                     | 32 +++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 examples/indexeddb-invalidstate.html

diff --git a/examples/indexeddb-invalidstate.html b/examples/indexeddb-invalidstate.html
new file mode 100644
index 0000000..578bf86
--- /dev/null
+++ b/examples/indexeddb-invalidstate.html
@@ -0,0 +1,38 @@
+<!doctype html>
+<html>
+  <head>
+    <meta charset="utf8" />
+    <title>Simple localForage example</title>
+  </head>
+  <body>
+    <script src="../dist/localforage.js"></script>
+    <script>
+      // Forcing localstorage here. Feel free to switch to other drivers :)
+      localforage.setDriver(localforage.INDEXEDDB).then(function() {
+        var key = 'STORE_KEY';
+        // var value = 'What we save offline';
+        var value = new Uint8Array(8);
+        value[0] = 65
+        // var value = undefined;
+        var UNKNOWN_KEY = 'unknown_key';
+
+        localforage.setItem(key, value, function() {
+          console.log('Saved: ' + value);
+
+          localforage._dbInfo.db.close();
+
+          localforage.getItem(key).then(function(readValue) {
+            console.log('Read: ', readValue);
+          }).catch(function(err) {
+            console.error('Read: ', err);
+          });
+
+          // Since this key hasn't been set yet, we'll get a null value
+          localforage.getItem(UNKNOWN_KEY, function(err, readValue) {
+            console.log('Result of reading ' + UNKNOWN_KEY, readValue);
+          });
+        });
+      });
+    </script>
+  </body>
+</html>
diff --git a/test/test.api.js b/test/test.api.js
index 71b897e..63a07cc 100644
--- a/test/test.api.js
+++ b/test/test.api.js
@@ -264,6 +264,38 @@ DRIVERS.forEach(function(driverName) {
                     localforage._dbInfo.db.transaction = transaction;
                 });
             });
+
+            describe('recover (reconnect) from IDBDatabase InvalidStateError', function() {
+
+                beforeEach(function(done) {
+                    localforage.setItem('key', 'value1').then(function() {
+                        localforage._dbInfo.db.close();
+                        done();
+                    }, function(error) {
+                        done(error || 'error');
+                    });
+                });
+
+                it('retrieves an item from the storage', function(done) {
+                    localforage.getItem('key').then(function(value) {
+                        expect(value).to.be('value1');
+                        done();
+                    }, function(error) {
+                        done(error || 'error');
+                    });
+                });
+
+                it('stores and retrieves an item from the storage', function(done) {
+                    localforage.setItem('key', 'value2').then(function() {
+                        return localforage.getItem('key');
+                    }).then(function(value) {
+                        expect(value).to.be('value2');
+                        done();
+                    }, function(error) {
+                        done(error || 'error');
+                    });
+                });
+            });
         }
 
         if (driverName === localforage.WEBSQL) {

From 7f75f07f8f93ae41e9a78a154719e47f1f2a2334 Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sat, 6 May 2017 15:16:19 +0300
Subject: [PATCH 03/10] fix(indexeddb): check db existence before closing

---
 src/drivers/indexeddb.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/drivers/indexeddb.js b/src/drivers/indexeddb.js
index b27d276..c2b4201 100644
--- a/src/drivers/indexeddb.js
+++ b/src/drivers/indexeddb.js
@@ -285,8 +285,10 @@ function _tryReconnect(dbInfo) {
     var forages = dbContext.forages;
 
     for (var i = 0; i < forages.length; i++) {
-        forages[i]._dbInfo.db.close();
-        forages[i]._dbInfo.db = null;
+        if (forages[i]._dbInfo.db) {
+            forages[i]._dbInfo.db.close();
+            forages[i]._dbInfo.db = null;
+        }
     }
 
     return _getConnection(dbInfo, false).then(function(db) {

From 1d17b300ad0a9fd0b7c6c831a1b8d74a92baead7 Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sun, 7 May 2017 10:55:52 +0300
Subject: [PATCH 04/10] fix(indexeddb): try re-establish DB connection using
 callbacks

---
 src/drivers/indexeddb.js | 409 ++++++++++++++++++++++-----------------
 1 file changed, 236 insertions(+), 173 deletions(-)

diff --git a/src/drivers/indexeddb.js b/src/drivers/indexeddb.js
index c2b4201..a06ecfc 100644
--- a/src/drivers/indexeddb.js
+++ b/src/drivers/indexeddb.js
@@ -301,23 +301,27 @@ function _tryReconnect(dbInfo) {
     });
 }
 
-function createTransaction(dbInfo, mode) {
+
+// FF doesn't like Promises (micro-tasks) and IDDB store operations,
+// so we have to do it with callbacks
+function createTransaction(dbInfo, mode, callback) {
     try {
         var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
-        return Promise.resolve(tx);
+        callback(null, tx);
     } catch (err) {
         if (err.name === 'InvalidStateError') {
             return _tryReconnect(dbInfo).then(function() {
 
                 var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
-                return Promise.resolve(tx);
+                callback(null, tx);
             });
         }
 
-        return Promise.reject(err);
+        callback(err);
     }
 }
 
+
 // Open the IndexedDB database (automatically creates one if one didn't
 // previously exist), using any options set in the config.
 function _initStorage(options) {
@@ -424,25 +428,33 @@ function getItem(key, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            return createTransaction(self._dbInfo, 'readonly');
-        }).then(function(transaction) {
-            var store = transaction.objectStore(self._dbInfo.storeName);
-            var req = store.get(key);
-
-            req.onsuccess = function() {
-                var value = req.result;
-                if (value === undefined) {
-                    value = null;
+            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
-                if (_isEncodedBlob(value)) {
-                    value = _decodeBlob(value);
-                }
-                resolve(value);
-            };
 
-            req.onerror = function() {
-                reject(req.error);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.get(key);
+
+                    req.onsuccess = function() {
+                        var value = req.result;
+                        if (value === undefined) {
+                            value = null;
+                        }
+                        if (_isEncodedBlob(value)) {
+                            value = _decodeBlob(value);
+                        }
+                        resolve(value);
+                    };
+
+                    req.onerror = function() {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 
@@ -456,36 +468,44 @@ function iterate(iterator, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            return createTransaction(self._dbInfo, 'readonly');
-        }).then(function(transaction) {
-            var store = transaction.objectStore(self._dbInfo.storeName);
-            var req = store.openCursor();
-            var iterationNumber = 1;
-
-            req.onsuccess = function() {
-                var cursor = req.result;
-
-                if (cursor) {
-                    var value = cursor.value;
-                    if (_isEncodedBlob(value)) {
-                        value = _decodeBlob(value);
-                    }
-                    var result = iterator(value, cursor.key,
-                        iterationNumber++);
-
-                    if (result !== void(0)) {
-                        resolve(result);
-                    } else {
-                        cursor.continue();
-                    }
-                } else {
-                    resolve();
+            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
-            };
 
-            req.onerror = function() {
-                reject(req.error);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.openCursor();
+                    var iterationNumber = 1;
+
+                    req.onsuccess = function() {
+                        var cursor = req.result;
+
+                        if (cursor) {
+                            var value = cursor.value;
+                            if (_isEncodedBlob(value)) {
+                                value = _decodeBlob(value);
+                            }
+                            var result = iterator(value, cursor.key,
+                                iterationNumber++);
+
+                            if (result !== void(0)) {
+                                resolve(result);
+                            } else {
+                                cursor.continue();
+                            }
+                        } else {
+                            resolve();
+                        }
+                    };
+
+                    req.onerror = function() {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 
@@ -518,40 +538,44 @@ function setItem(key, value, callback) {
             }
             return value;
         }).then(function(value) {
-            return createTransaction(self._dbInfo, 'readwrite').then(function(transaction) {
-                return [transaction, value];
-            });
-        }).then(function(txAndValue) {
-            var transaction = txAndValue[0];
-            var value = txAndValue[1];
-            var store = transaction.objectStore(self._dbInfo.storeName);
-            var req = store.put(value, key);
-
-            // The reason we don't _save_ null is because IE 10 does
-            // not support saving the `null` type in IndexedDB. How
-            // ironic, given the bug below!
-            // See: https://github.com/mozilla/localForage/issues/161
-            if (value === null) {
-                value = undefined;
-            }
-
-            transaction.oncomplete = function() {
-                // Cast to undefined so the value passed to
-                // callback/promise is the same as what one would get out
-                // of `getItem()` later. This leads to some weirdness
-                // (setItem('foo', undefined) will return `null`), but
-                // it's not my fault localStorage is our baseline and that
-                // it's weird.
-                if (value === undefined) {
-                    value = null;
+            createTransaction(self._dbInfo, 'readwrite', function(err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                resolve(value);
-            };
-            transaction.onabort = transaction.onerror = function() {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.put(value, key);
+
+                    // The reason we don't _save_ null is because IE 10 does
+                    // not support saving the `null` type in IndexedDB. How
+                    // ironic, given the bug below!
+                    // See: https://github.com/mozilla/localForage/issues/161
+                    if (value === null) {
+                        value = undefined;
+                    }
+
+                    transaction.oncomplete = function() {
+                        // Cast to undefined so the value passed to
+                        // callback/promise is the same as what one would get out
+                        // of `getItem()` later. This leads to some weirdness
+                        // (setItem('foo', undefined) will return `null`), but
+                        // it's not my fault localStorage is our baseline and that
+                        // it's weird.
+                        if (value === undefined) {
+                            value = null;
+                        }
+
+                        resolve(value);
+                    };
+                    transaction.onabort = transaction.onerror = function() {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 
@@ -571,30 +595,37 @@ function removeItem(key, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            return createTransaction(self._dbInfo, 'readwrite');
-        }).then(function(transaction) {
-            var store = transaction.objectStore(self._dbInfo.storeName);
+            createTransaction(self._dbInfo, 'readwrite', function(err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            // We use a Grunt task to make this safe for IE and some
-            // versions of Android (including those used by Cordova).
-            // Normally IE won't like `.delete()` and will insist on
-            // using `['delete']()`, but we have a build step that
-            // fixes this for us now.
-            var req = store.delete(key);
-            transaction.oncomplete = function() {
-                resolve();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    // We use a Grunt task to make this safe for IE and some
+                    // versions of Android (including those used by Cordova).
+                    // Normally IE won't like `.delete()` and will insist on
+                    // using `['delete']()`, but we have a build step that
+                    // fixes this for us now.
+                    var req = store.delete(key);
+                    transaction.oncomplete = function() {
+                        resolve();
+                    };
 
-            transaction.onerror = function() {
-                reject(req.error);
-            };
+                    transaction.onerror = function() {
+                        reject(req.error);
+                    };
 
-            // The request will be also be aborted if we've exceeded our storage
-            // space.
-            transaction.onabort = function() {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                    // The request will be also be aborted if we've exceeded our storage
+                    // space.
+                    transaction.onabort = function() {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 
@@ -607,19 +638,27 @@ function clear(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            return createTransaction(self._dbInfo, 'readwrite');
-        }).then(function(transaction) {
-            var store = transaction.objectStore(self._dbInfo.storeName);
-            var req = store.clear();
+            createTransaction(self._dbInfo, 'readwrite', function(err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            transaction.oncomplete = function() {
-                resolve();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.clear();
 
-            transaction.onabort = transaction.onerror = function() {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                    transaction.oncomplete = function() {
+                        resolve();
+                    };
+
+                    transaction.onabort = transaction.onerror = function() {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 
@@ -632,18 +671,26 @@ function length(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            return createTransaction(self._dbInfo, 'readonly');
-        }).then(function(transaction) {
-            var store = transaction.objectStore(self._dbInfo.storeName);
-            var req = store.count();
+            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            req.onsuccess = function() {
-                resolve(req.result);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.count();
 
-            req.onerror = function() {
-                reject(req.error);
-            };
+                    req.onsuccess = function() {
+                        resolve(req.result);
+                    };
+
+                    req.onerror = function() {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 
@@ -662,41 +709,49 @@ function key(n, callback) {
         }
 
         self.ready().then(function() {
-            return createTransaction(self._dbInfo, 'readonly');
-        }).then(function(transaction) {
-            var store = transaction.objectStore(self._dbInfo.storeName);
-            var advanced = false;
-            var req = store.openCursor();
-
-            req.onsuccess = function() {
-                var cursor = req.result;
-                if (!cursor) {
-                    // this means there weren't enough keys
-                    resolve(null);
-
-                    return;
+            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                if (n === 0) {
-                    // We have the first key, return it if that's what they
-                    // wanted.
-                    resolve(cursor.key);
-                } else {
-                    if (!advanced) {
-                        // Otherwise, ask the cursor to skip ahead n
-                        // records.
-                        advanced = true;
-                        cursor.advance(n);
-                    } else {
-                        // When we get here, we've got the nth key.
-                        resolve(cursor.key);
-                    }
-                }
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var advanced = false;
+                    var req = store.openCursor();
 
-            req.onerror = function() {
-                reject(req.error);
-            };
+                    req.onsuccess = function() {
+                        var cursor = req.result;
+                        if (!cursor) {
+                            // this means there weren't enough keys
+                            resolve(null);
+
+                            return;
+                        }
+
+                        if (n === 0) {
+                            // We have the first key, return it if that's what they
+                            // wanted.
+                            resolve(cursor.key);
+                        } else {
+                            if (!advanced) {
+                                // Otherwise, ask the cursor to skip ahead n
+                                // records.
+                                advanced = true;
+                                cursor.advance(n);
+                            } else {
+                                // When we get here, we've got the nth key.
+                                resolve(cursor.key);
+                            }
+                        }
+                    };
+
+                    req.onerror = function() {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 
@@ -709,27 +764,35 @@ function keys(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            return createTransaction(self._dbInfo, 'readonly');
-        }).then(function(transaction) {
-            var store = transaction.objectStore(self._dbInfo.storeName);
-            var req = store.openCursor();
-            var keys = [];
-
-            req.onsuccess = function() {
-                var cursor = req.result;
-
-                if (!cursor) {
-                    resolve(keys);
-                    return;
+            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                keys.push(cursor.key);
-                cursor.continue();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.openCursor();
+                    var keys = [];
 
-            req.onerror = function() {
-                reject(req.error);
-            };
+                    req.onsuccess = function() {
+                        var cursor = req.result;
+
+                        if (!cursor) {
+                            resolve(keys);
+                            return;
+                        }
+
+                        keys.push(cursor.key);
+                        cursor.continue();
+                    };
+
+                    req.onerror = function() {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         }).catch(reject);
     });
 

From 85bc1d2c5f9ef2ef578cf5838b27eccf43b79d04 Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sun, 14 May 2017 12:43:17 +0300
Subject: [PATCH 05/10] style(examples/indexeddb-invalidstate): remove some
 comments

---
 examples/indexeddb-invalidstate.html | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/examples/indexeddb-invalidstate.html b/examples/indexeddb-invalidstate.html
index 578bf86..cb49cc7 100644
--- a/examples/indexeddb-invalidstate.html
+++ b/examples/indexeddb-invalidstate.html
@@ -7,18 +7,17 @@
   <body>
     <script src="../dist/localforage.js"></script>
     <script>
-      // Forcing localstorage here. Feel free to switch to other drivers :)
+      // Forcing IndexedDB here.
       localforage.setDriver(localforage.INDEXEDDB).then(function() {
         var key = 'STORE_KEY';
-        // var value = 'What we save offline';
         var value = new Uint8Array(8);
         value[0] = 65
-        // var value = undefined;
         var UNKNOWN_KEY = 'unknown_key';
 
         localforage.setItem(key, value, function() {
           console.log('Saved: ' + value);
 
+          // causes InvalidState erros
           localforage._dbInfo.db.close();
 
           localforage.getItem(key).then(function(readValue) {
@@ -28,7 +27,7 @@
           });
 
           // Since this key hasn't been set yet, we'll get a null value
-          localforage.getItem(UNKNOWN_KEY, function(err, readValue) {
+          localforage.getItem(UNKNOWN_KEY).then(function(err, readValue) {
             console.log('Result of reading ' + UNKNOWN_KEY, readValue);
           });
         });

From 60201b286e47fd248a8708c52e1aedb863089556 Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sun, 14 May 2017 15:11:24 +0300
Subject: [PATCH 06/10] test(api): test IDBD concurrent requests after
 InvalidStateError

---
 test/test.api.js | 51 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 48 insertions(+), 3 deletions(-)

diff --git a/test/test.api.js b/test/test.api.js
index 63a07cc..4132be3 100644
--- a/test/test.api.js
+++ b/test/test.api.js
@@ -268,7 +268,12 @@ DRIVERS.forEach(function(driverName) {
             describe('recover (reconnect) from IDBDatabase InvalidStateError', function() {
 
                 beforeEach(function(done) {
-                    localforage.setItem('key', 'value1').then(function() {
+                    Promise.all([
+                        localforage.setItem('key', 'value1'),
+                        localforage.setItem('key1', 'value1'),
+                        localforage.setItem('key2', 'value2'),
+                        localforage.setItem('key3', 'value3')
+                    ]).then(function() {
                         localforage._dbInfo.db.close();
                         done();
                     }, function(error) {
@@ -285,11 +290,51 @@ DRIVERS.forEach(function(driverName) {
                     });
                 });
 
+                it('retrieves more than one items from the storage', function(done) {
+                    Promise.all([
+                        localforage.getItem('key1'),
+                        localforage.getItem('key2'),
+                        localforage.getItem('key3')
+                    ]).then(function(values) {
+                        expect(values).to.eql([
+                            'value1',
+                            'value2',
+                            'value3'
+                        ]);
+                        done();
+                    }, function(error) {
+                        done(error || 'error');
+                    });
+                });
+
                 it('stores and retrieves an item from the storage', function(done) {
-                    localforage.setItem('key', 'value2').then(function() {
+                    localforage.setItem('key', 'value1b').then(function() {
                         return localforage.getItem('key');
                     }).then(function(value) {
-                        expect(value).to.be('value2');
+                        expect(value).to.be('value1b');
+                        done();
+                    }, function(error) {
+                        done(error || 'error');
+                    });
+                });
+
+                it('stores and retrieves more than one items from the storage', function(done) {
+                    Promise.all([
+                        localforage.setItem('key1', 'value1b'),
+                        localforage.setItem('key2', 'value2b'),
+                        localforage.setItem('key3', 'value3b')
+                    ]).then(function() {
+                        return Promise.all([
+                            localforage.getItem('key1'),
+                            localforage.getItem('key2'),
+                            localforage.getItem('key3')
+                        ]);
+                    }).then(function(values) {
+                        expect(values).to.eql([
+                            'value1b',
+                            'value2b',
+                            'value3b'
+                        ]);
                         done();
                     }, function(error) {
                         done(error || 'error');

From 4db9f4a559a41997d92ec934aaaea38d0e9bbb47 Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sun, 14 May 2017 15:12:59 +0300
Subject: [PATCH 07/10] fix(indexeddb): fix concurrent requests after
 InvalidStateError

---
 src/drivers/indexeddb.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/drivers/indexeddb.js b/src/drivers/indexeddb.js
index a06ecfc..10997b6 100644
--- a/src/drivers/indexeddb.js
+++ b/src/drivers/indexeddb.js
@@ -309,7 +309,8 @@ function createTransaction(dbInfo, mode, callback) {
         var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
         callback(null, tx);
     } catch (err) {
-        if (err.name === 'InvalidStateError') {
+        if (!dbInfo.db ||
+            err.name === 'InvalidStateError') {
             return _tryReconnect(dbInfo).then(function() {
 
                 var tx = dbInfo.db.transaction(dbInfo.storeName, mode);

From d326185c864dd57a2c5d0743b4443ce2e61672ee Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sun, 14 May 2017 15:19:38 +0300
Subject: [PATCH 08/10] style(indexeddb): add comment about iterator early exit

---
 src/drivers/indexeddb.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/drivers/indexeddb.js b/src/drivers/indexeddb.js
index 10997b6..ddb2e32 100644
--- a/src/drivers/indexeddb.js
+++ b/src/drivers/indexeddb.js
@@ -490,6 +490,9 @@ function iterate(iterator, callback) {
                             var result = iterator(value, cursor.key,
                                 iterationNumber++);
 
+                            // when the iterator callback retuns any
+                            // (non-`undefined`) value, then we stop
+                            // the iteration immediately
                             if (result !== void(0)) {
                                 resolve(result);
                             } else {

From 719b74dc1f1e5b5dbbcbdb624cf724d94cd01b6a Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sun, 14 May 2017 15:24:06 +0300
Subject: [PATCH 09/10] refactor(indexeddb): use consts for the Transaction
 modes

---
 src/drivers/indexeddb.js | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/drivers/indexeddb.js b/src/drivers/indexeddb.js
index ddb2e32..7cc54c6 100644
--- a/src/drivers/indexeddb.js
+++ b/src/drivers/indexeddb.js
@@ -12,6 +12,10 @@ var supportsBlobs;
 var dbContexts;
 var toString = Object.prototype.toString;
 
+// Transaction Modes
+var READ_ONLY = 'readonly';
+var READ_WRITE = 'readwrite';
+
 // Transform a binary string to an array buffer, because otherwise
 // weird stuff happens when you try to work with the binary string directly.
 // It is known.
@@ -44,7 +48,7 @@ function _binStringToArrayBuffer(bin) {
 //
 function _checkBlobSupportWithoutCaching(idb) {
     return new Promise(function(resolve) {
-        var txn = idb.transaction(DETECT_BLOB_SUPPORT_STORE, 'readwrite');
+        var txn = idb.transaction(DETECT_BLOB_SUPPORT_STORE, READ_WRITE);
         var blob = createBlob(['']);
         txn.objectStore(DETECT_BLOB_SUPPORT_STORE).put(blob, 'key');
 
@@ -429,7 +433,7 @@ function getItem(key, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_ONLY, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }
@@ -469,7 +473,7 @@ function iterate(iterator, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_ONLY, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }
@@ -542,7 +546,7 @@ function setItem(key, value, callback) {
             }
             return value;
         }).then(function(value) {
-            createTransaction(self._dbInfo, 'readwrite', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_WRITE, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }
@@ -599,7 +603,7 @@ function removeItem(key, callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            createTransaction(self._dbInfo, 'readwrite', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_WRITE, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }
@@ -642,7 +646,7 @@ function clear(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            createTransaction(self._dbInfo, 'readwrite', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_WRITE, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }
@@ -675,7 +679,7 @@ function length(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_ONLY, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }
@@ -713,7 +717,7 @@ function key(n, callback) {
         }
 
         self.ready().then(function() {
-            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_ONLY, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }
@@ -768,7 +772,7 @@ function keys(callback) {
 
     var promise = new Promise(function(resolve, reject) {
         self.ready().then(function() {
-            createTransaction(self._dbInfo, 'readonly', function(err, transaction) {
+            createTransaction(self._dbInfo, READ_ONLY, function(err, transaction) {
                 if (err) {
                     return reject(err);
                 }

From 6c159b8e6b082aa4275530694d374afce6bc2999 Mon Sep 17 00:00:00 2001
From: Thodoris Greasidis <thgreasi@gmail.com>
Date: Sun, 14 May 2017 15:42:23 +0300
Subject: [PATCH 10/10] chore: add dist for IDB InvalidStateError reconnect

---
 dist/localforage.js                | 454 +++++++++++++++++++----------
 dist/localforage.min.js            |   2 +-
 dist/localforage.nopromises.js     | 454 +++++++++++++++++++----------
 dist/localforage.nopromises.min.js |   2 +-
 4 files changed, 588 insertions(+), 324 deletions(-)

diff --git a/dist/localforage.js b/dist/localforage.js
index 9fc8867..6c028ed 100644
--- a/dist/localforage.js
+++ b/dist/localforage.js
@@ -470,6 +470,10 @@ var supportsBlobs;
 var dbContexts;
 var toString = Object.prototype.toString;
 
+// Transaction Modes
+var READ_ONLY = 'readonly';
+var READ_WRITE = 'readwrite';
+
 // Transform a binary string to an array buffer, because otherwise
 // weird stuff happens when you try to work with the binary string directly.
 // It is known.
@@ -502,7 +506,7 @@ function _binStringToArrayBuffer(bin) {
 //
 function _checkBlobSupportWithoutCaching(idb) {
     return new Promise$1(function (resolve) {
-        var txn = idb.transaction(DETECT_BLOB_SUPPORT_STORE, 'readwrite');
+        var txn = idb.transaction(DETECT_BLOB_SUPPORT_STORE, READ_WRITE);
         var blob = createBlob(['']);
         txn.objectStore(DETECT_BLOB_SUPPORT_STORE).put(blob, 'key');
 
@@ -572,6 +576,19 @@ function _advanceReadiness(dbInfo) {
     }
 }
 
+function _rejectReadiness(dbInfo, err) {
+    var dbContext = dbContexts[dbInfo.name];
+
+    // Dequeue a deferred operation.
+    var deferredOperation = dbContext.deferredOperations.pop();
+
+    // Reject its promise (which is part of the database readiness
+    // chain of promises).
+    if (deferredOperation) {
+        deferredOperation.reject(err);
+    }
+}
+
 function _getConnection(dbInfo, upgradeNeeded) {
     return new Promise$1(function (resolve, reject) {
 
@@ -714,6 +731,51 @@ function _fullyReady(callback) {
     return promise;
 }
 
+// Try to establish a new db connection to replace the
+// current one which is broken (i.e. experiencing
+// InvalidStateError while creating a transaction).
+function _tryReconnect(dbInfo) {
+    _deferReadiness(dbInfo);
+
+    var dbContext = dbContexts[dbInfo.name];
+    var forages = dbContext.forages;
+
+    for (var i = 0; i < forages.length; i++) {
+        if (forages[i]._dbInfo.db) {
+            forages[i]._dbInfo.db.close();
+            forages[i]._dbInfo.db = null;
+        }
+    }
+
+    return _getConnection(dbInfo, false).then(function (db) {
+        for (var j = 0; j < forages.length; j++) {
+            forages[j]._dbInfo.db = db;
+        }
+    })["catch"](function (err) {
+        _rejectReadiness(dbInfo, err);
+        throw err;
+    });
+}
+
+// FF doesn't like Promises (micro-tasks) and IDDB store operations,
+// so we have to do it with callbacks
+function createTransaction(dbInfo, mode, callback) {
+    try {
+        var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
+        callback(null, tx);
+    } catch (err) {
+        if (!dbInfo.db || err.name === 'InvalidStateError') {
+            return _tryReconnect(dbInfo).then(function () {
+
+                var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
+                callback(null, tx);
+            });
+        }
+
+        callback(err);
+    }
+}
+
 // Open the IndexedDB database (automatically creates one if one didn't
 // previously exist), using any options set in the config.
 function _initStorage(options) {
@@ -820,24 +882,33 @@ function getItem(key, callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-            var req = store.get(key);
-
-            req.onsuccess = function () {
-                var value = req.result;
-                if (value === undefined) {
-                    value = null;
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
-                if (_isEncodedBlob(value)) {
-                    value = _decodeBlob(value);
-                }
-                resolve(value);
-            };
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.get(key);
+
+                    req.onsuccess = function () {
+                        var value = req.result;
+                        if (value === undefined) {
+                            value = null;
+                        }
+                        if (_isEncodedBlob(value)) {
+                            value = _decodeBlob(value);
+                        }
+                        resolve(value);
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -851,35 +922,46 @@ function iterate(iterator, callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-
-            var req = store.openCursor();
-            var iterationNumber = 1;
-
-            req.onsuccess = function () {
-                var cursor = req.result;
-
-                if (cursor) {
-                    var value = cursor.value;
-                    if (_isEncodedBlob(value)) {
-                        value = _decodeBlob(value);
-                    }
-                    var result = iterator(value, cursor.key, iterationNumber++);
-
-                    if (result !== void 0) {
-                        resolve(result);
-                    } else {
-                        cursor["continue"]();
-                    }
-                } else {
-                    resolve();
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
-            };
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.openCursor();
+                    var iterationNumber = 1;
+
+                    req.onsuccess = function () {
+                        var cursor = req.result;
+
+                        if (cursor) {
+                            var value = cursor.value;
+                            if (_isEncodedBlob(value)) {
+                                value = _decodeBlob(value);
+                            }
+                            var result = iterator(value, cursor.key, iterationNumber++);
+
+                            // when the iterator callback retuns any
+                            // (non-`undefined`) value, then we stop
+                            // the iteration immediately
+                            if (result !== void 0) {
+                                resolve(result);
+                            } else {
+                                cursor["continue"]();
+                            }
+                        } else {
+                            resolve();
+                        }
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -911,35 +993,44 @@ function setItem(key, value, callback) {
             }
             return value;
         }).then(function (value) {
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
-            var req = store.put(value, key);
-
-            // The reason we don't _save_ null is because IE 10 does
-            // not support saving the `null` type in IndexedDB. How
-            // ironic, given the bug below!
-            // See: https://github.com/mozilla/localForage/issues/161
-            if (value === null) {
-                value = undefined;
-            }
-
-            transaction.oncomplete = function () {
-                // Cast to undefined so the value passed to
-                // callback/promise is the same as what one would get out
-                // of `getItem()` later. This leads to some weirdness
-                // (setItem('foo', undefined) will return `null`), but
-                // it's not my fault localStorage is our baseline and that
-                // it's weird.
-                if (value === undefined) {
-                    value = null;
+            createTransaction(self._dbInfo, READ_WRITE, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                resolve(value);
-            };
-            transaction.onabort = transaction.onerror = function () {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.put(value, key);
+
+                    // The reason we don't _save_ null is because IE 10 does
+                    // not support saving the `null` type in IndexedDB. How
+                    // ironic, given the bug below!
+                    // See: https://github.com/mozilla/localForage/issues/161
+                    if (value === null) {
+                        value = undefined;
+                    }
+
+                    transaction.oncomplete = function () {
+                        // Cast to undefined so the value passed to
+                        // callback/promise is the same as what one would get out
+                        // of `getItem()` later. This leads to some weirdness
+                        // (setItem('foo', undefined) will return `null`), but
+                        // it's not my fault localStorage is our baseline and that
+                        // it's weird.
+                        if (value === undefined) {
+                            value = null;
+                        }
+
+                        resolve(value);
+                    };
+                    transaction.onabort = transaction.onerror = function () {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -958,30 +1049,37 @@ function removeItem(key, callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
+            createTransaction(self._dbInfo, READ_WRITE, function (err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            // We use a Grunt task to make this safe for IE and some
-            // versions of Android (including those used by Cordova).
-            // Normally IE won't like `.delete()` and will insist on
-            // using `['delete']()`, but we have a build step that
-            // fixes this for us now.
-            var req = store["delete"](key);
-            transaction.oncomplete = function () {
-                resolve();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    // We use a Grunt task to make this safe for IE and some
+                    // versions of Android (including those used by Cordova).
+                    // Normally IE won't like `.delete()` and will insist on
+                    // using `['delete']()`, but we have a build step that
+                    // fixes this for us now.
+                    var req = store["delete"](key);
+                    transaction.oncomplete = function () {
+                        resolve();
+                    };
 
-            transaction.onerror = function () {
-                reject(req.error);
-            };
+                    transaction.onerror = function () {
+                        reject(req.error);
+                    };
 
-            // The request will be also be aborted if we've exceeded our storage
-            // space.
-            transaction.onabort = function () {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                    // The request will be also be aborted if we've exceeded our storage
+                    // space.
+                    transaction.onabort = function () {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -994,19 +1092,27 @@ function clear(callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
-            var req = store.clear();
+            createTransaction(self._dbInfo, READ_WRITE, function (err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            transaction.oncomplete = function () {
-                resolve();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.clear();
 
-            transaction.onabort = transaction.onerror = function () {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                    transaction.oncomplete = function () {
+                        resolve();
+                    };
+
+                    transaction.onabort = transaction.onerror = function () {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -1019,17 +1125,26 @@ function length(callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-            var req = store.count();
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            req.onsuccess = function () {
-                resolve(req.result);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.count();
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                    req.onsuccess = function () {
+                        resolve(req.result);
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -1048,40 +1163,49 @@ function key(n, callback) {
         }
 
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-
-            var advanced = false;
-            var req = store.openCursor();
-            req.onsuccess = function () {
-                var cursor = req.result;
-                if (!cursor) {
-                    // this means there weren't enough keys
-                    resolve(null);
-
-                    return;
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                if (n === 0) {
-                    // We have the first key, return it if that's what they
-                    // wanted.
-                    resolve(cursor.key);
-                } else {
-                    if (!advanced) {
-                        // Otherwise, ask the cursor to skip ahead n
-                        // records.
-                        advanced = true;
-                        cursor.advance(n);
-                    } else {
-                        // When we get here, we've got the nth key.
-                        resolve(cursor.key);
-                    }
-                }
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var advanced = false;
+                    var req = store.openCursor();
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                    req.onsuccess = function () {
+                        var cursor = req.result;
+                        if (!cursor) {
+                            // this means there weren't enough keys
+                            resolve(null);
+
+                            return;
+                        }
+
+                        if (n === 0) {
+                            // We have the first key, return it if that's what they
+                            // wanted.
+                            resolve(cursor.key);
+                        } else {
+                            if (!advanced) {
+                                // Otherwise, ask the cursor to skip ahead n
+                                // records.
+                                advanced = true;
+                                cursor.advance(n);
+                            } else {
+                                // When we get here, we've got the nth key.
+                                resolve(cursor.key);
+                            }
+                        }
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -1094,27 +1218,35 @@ function keys(callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-
-            var req = store.openCursor();
-            var keys = [];
-
-            req.onsuccess = function () {
-                var cursor = req.result;
-
-                if (!cursor) {
-                    resolve(keys);
-                    return;
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                keys.push(cursor.key);
-                cursor["continue"]();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.openCursor();
+                    var keys = [];
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                    req.onsuccess = function () {
+                        var cursor = req.result;
+
+                        if (!cursor) {
+                            resolve(keys);
+                            return;
+                        }
+
+                        keys.push(cursor.key);
+                        cursor["continue"]();
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
diff --git a/dist/localforage.min.js b/dist/localforage.min.js
index db9faa4..8c4142c 100644
--- a/dist/localforage.min.js
+++ b/dist/localforage.min.js
@@ -4,4 +4,4 @@
     https://localforage.github.io/localForage
     (c) 2013-2017 Mozilla, Apache License 2.0
 */
-!function(a){if("object"==typeof exports&&"undefined"!=typeof module)module.exports=a();else if("function"==typeof define&&define.amd)define([],a);else{var b;b="undefined"!=typeof window?window:"undefined"!=typeof global?global:"undefined"!=typeof self?self:this,b.localforage=a()}}(function(){return function a(b,c,d){function e(g,h){if(!c[g]){if(!b[g]){var i="function"==typeof require&&require;if(!h&&i)return i(g,!0);if(f)return f(g,!0);var j=new Error("Cannot find module '"+g+"'");throw j.code="MODULE_NOT_FOUND",j}var k=c[g]={exports:{}};b[g][0].call(k.exports,function(a){var c=b[g][1][a];return e(c||a)},k,k.exports,a,b,c,d)}return c[g].exports}for(var f="function"==typeof require&&require,g=0;g<d.length;g++)e(d[g]);return e}({1:[function(a,b,c){(function(a){"use strict";function c(){k=!0;for(var a,b,c=l.length;c;){for(b=l,l=[],a=-1;++a<c;)b[a]();c=l.length}k=!1}function d(a){1!==l.push(a)||k||e()}var e,f=a.MutationObserver||a.WebKitMutationObserver;if(f){var g=0,h=new f(c),i=a.document.createTextNode("");h.observe(i,{characterData:!0}),e=function(){i.data=g=++g%2}}else if(a.setImmediate||void 0===a.MessageChannel)e="document"in a&&"onreadystatechange"in a.document.createElement("script")?function(){var b=a.document.createElement("script");b.onreadystatechange=function(){c(),b.onreadystatechange=null,b.parentNode.removeChild(b),b=null},a.document.documentElement.appendChild(b)}:function(){setTimeout(c,0)};else{var j=new a.MessageChannel;j.port1.onmessage=c,e=function(){j.port2.postMessage(0)}}var k,l=[];b.exports=d}).call(this,"undefined"!=typeof global?global:"undefined"!=typeof self?self:"undefined"!=typeof window?window:{})},{}],2:[function(a,b,c){"use strict";function d(){}function e(a){if("function"!=typeof a)throw new TypeError("resolver must be a function");this.state=s,this.queue=[],this.outcome=void 0,a!==d&&i(this,a)}function f(a,b,c){this.promise=a,"function"==typeof b&&(this.onFulfilled=b,this.callFulfilled=this.otherCallFulfilled),"function"==typeof c&&(this.onRejected=c,this.callRejected=this.otherCallRejected)}function g(a,b,c){o(function(){var d;try{d=b(c)}catch(b){return p.reject(a,b)}d===a?p.reject(a,new TypeError("Cannot resolve promise with itself")):p.resolve(a,d)})}function h(a){var b=a&&a.then;if(a&&"object"==typeof a&&"function"==typeof b)return function(){b.apply(a,arguments)}}function i(a,b){function c(b){f||(f=!0,p.reject(a,b))}function d(b){f||(f=!0,p.resolve(a,b))}function e(){b(d,c)}var f=!1,g=j(e);"error"===g.status&&c(g.value)}function j(a,b){var c={};try{c.value=a(b),c.status="success"}catch(a){c.status="error",c.value=a}return c}function k(a){return a instanceof this?a:p.resolve(new this(d),a)}function l(a){var b=new this(d);return p.reject(b,a)}function m(a){function b(a,b){function d(a){g[b]=a,++h!==e||f||(f=!0,p.resolve(j,g))}c.resolve(a).then(d,function(a){f||(f=!0,p.reject(j,a))})}var c=this;if("[object 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c=!a.db.objectStoreNames.contains(a.storeName),d=a.version<a.db.version,e=a.version>a.db.version;if(d&&(a.version!==b&&console.warn('The database "'+a.name+"\" can't be downgraded from version "+a.db.version+" to version "+a.version+"."),a.version=a.db.version),e||c){if(c){var f=a.db.version+1;f>a.version&&(a.version=f)}return!0}return!1}function u(a){return new ja(function(b,c){var d=new FileReader;d.onerror=c,d.onloadend=function(c){var d=btoa(c.target.result||"");b({__local_forage_encoded_blob:!0,data:d,type:a.type})},d.readAsBinaryString(a)})}function v(a){return i([l(atob(a.data))],{type:a.type})}function w(a){return a&&a.__local_forage_encoded_blob}function x(a){var b=this,c=b._initReady().then(function(){var a=ia[b._dbInfo.name];if(a&&a.dbReady)return a.dbReady});return k(c,a,a),c}function y(a){function b(){return ja.resolve()}var c=this,d={db:null};if(a)for(var e in a)d[e]=a[e];ia||(ia={});var 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Ta=Array.isArray||function(a){return"[object Array]"===Object.prototype.toString.call(a)},Ua=function(){function a(b){d(this,a),this.INDEXEDDB=Oa.INDEXEDDB,this.LOCALSTORAGE=Oa.LOCALSTORAGE,this.WEBSQL=Oa.WEBSQL,this._defaultConfig=ga({},Ra),this._config=ga({},this._defaultConfig,b),this._driverSet=null,this._initDriver=null,this._ready=!1,this._dbInfo=null,this._wrapLibraryMethodsWithReady(),this.setDriver(this._config.driver).catch(function(){})}return a.prototype.config=function(a){if("object"===(void 0===a?"undefined":ia(a))){if(this._ready)return new Error("Can't call config() after localforage has been used.");for(var b in a){if("storeName"===b&&(a[b]=a[b].replace(/\W/g,"_")),"version"===b&&"number"!=typeof a[b])return new Error("Database version must be a number.");this._config[b]=a[b]}return!("driver"in a&&a.driver)||this.setDriver(this._config.driver)}return"string"==typeof a?this._config[a]:this._config},a.prototype.defineDriver=function(a,b,c){var d=new ma(function(b,c){try{var d=a._driver,e=new Error("Custom driver not compliant; see https://mozilla.github.io/localForage/#definedriver"),f=new Error("Custom driver name already in use: "+a._driver);if(!a._driver)return void c(e);if(ha(a._driver))return void c(f);for(var g=Qa.concat("_initStorage"),h=0;h<g.length;h++){var i=g[h];if(!i||!a[i]||"function"!=typeof a[i])return void c(e)}var j=function(c){Sa[d]=c,Na[d]=a,b()};"_support"in a?a._support&&"function"==typeof a._support?a._support().then(j,c):j(!!a._support):j(!0)}catch(a){c(a)}});return k(d,b,c),d},a.prototype.driver=function(){return this._driver||null},a.prototype.getDriver=function(a,b,c){var d=this,e=ma.resolve().then(function(){if(!ha(a)){if(Na[a])return Na[a];throw new Error("Driver not found.")}switch(a){case d.INDEXEDDB:return ra;case d.LOCALSTORAGE:return Ma;case d.WEBSQL:return La}});return k(e,b,c),e},a.prototype.getSerializer=function(a){var b=ma.resolve(Ka);return k(b,a),b},a.prototype.ready=function(a){var b=this,c=b._driverSet.then(function(){return null===b._ready&&(b._ready=b._initDriver()),b._ready});return k(c,a,a),c},a.prototype.setDriver=function(a,b,c){function d(){g._config.driver=g.driver()}function e(a){return g._extend(a),d(),g._ready=g._initStorage(g._config),g._ready}function f(a){return function(){function b(){for(;c<a.length;){var f=a[c];return c++,g._dbInfo=null,g._ready=null,g.getDriver(f).then(e).catch(b)}d();var h=new Error("No available storage method found.");return g._driverSet=ma.reject(h),g._driverSet}var c=0;return b()}}var g=this;Ta(a)||(a=[a]);var h=this._getSupportedDrivers(a),i=null!==this._driverSet?this._driverSet.catch(function(){return ma.resolve()}):ma.resolve();return this._driverSet=i.then(function(){var a=h[0];return g._dbInfo=null,g._ready=null,g.getDriver(a).then(function(a){g._driver=a._driver,d(),g._wrapLibraryMethodsWithReady(),g._initDriver=f(h)})}).catch(function(){d();var a=new Error("No available storage method found.");return g._driverSet=ma.reject(a),g._driverSet}),k(this._driverSet,b,c),this._driverSet},a.prototype.supports=function(a){return!!Sa[a]},a.prototype._extend=function(a){ga(this,a)},a.prototype._getSupportedDrivers=function(a){for(var b=[],c=0,d=a.length;c<d;c++){var e=a[c];this.supports(e)&&b.push(e)}return b},a.prototype._wrapLibraryMethodsWithReady=function(){for(var a=0;a<Qa.length;a++)fa(this,Qa[a])},a.prototype.createInstance=function(b){return new a(b)},a}(),Va=new Ua;b.exports=Va},{3:3}]},{},[4])(4)});
\ No newline at end of file
diff --git a/dist/localforage.nopromises.js b/dist/localforage.nopromises.js
index ba33a36..c0a782a 100644
--- a/dist/localforage.nopromises.js
+++ b/dist/localforage.nopromises.js
@@ -134,6 +134,10 @@ var supportsBlobs;
 var dbContexts;
 var toString = Object.prototype.toString;
 
+// Transaction Modes
+var READ_ONLY = 'readonly';
+var READ_WRITE = 'readwrite';
+
 // Transform a binary string to an array buffer, because otherwise
 // weird stuff happens when you try to work with the binary string directly.
 // It is known.
@@ -166,7 +170,7 @@ function _binStringToArrayBuffer(bin) {
 //
 function _checkBlobSupportWithoutCaching(idb) {
     return new Promise$1(function (resolve) {
-        var txn = idb.transaction(DETECT_BLOB_SUPPORT_STORE, 'readwrite');
+        var txn = idb.transaction(DETECT_BLOB_SUPPORT_STORE, READ_WRITE);
         var blob = createBlob(['']);
         txn.objectStore(DETECT_BLOB_SUPPORT_STORE).put(blob, 'key');
 
@@ -236,6 +240,19 @@ function _advanceReadiness(dbInfo) {
     }
 }
 
+function _rejectReadiness(dbInfo, err) {
+    var dbContext = dbContexts[dbInfo.name];
+
+    // Dequeue a deferred operation.
+    var deferredOperation = dbContext.deferredOperations.pop();
+
+    // Reject its promise (which is part of the database readiness
+    // chain of promises).
+    if (deferredOperation) {
+        deferredOperation.reject(err);
+    }
+}
+
 function _getConnection(dbInfo, upgradeNeeded) {
     return new Promise$1(function (resolve, reject) {
 
@@ -378,6 +395,51 @@ function _fullyReady(callback) {
     return promise;
 }
 
+// Try to establish a new db connection to replace the
+// current one which is broken (i.e. experiencing
+// InvalidStateError while creating a transaction).
+function _tryReconnect(dbInfo) {
+    _deferReadiness(dbInfo);
+
+    var dbContext = dbContexts[dbInfo.name];
+    var forages = dbContext.forages;
+
+    for (var i = 0; i < forages.length; i++) {
+        if (forages[i]._dbInfo.db) {
+            forages[i]._dbInfo.db.close();
+            forages[i]._dbInfo.db = null;
+        }
+    }
+
+    return _getConnection(dbInfo, false).then(function (db) {
+        for (var j = 0; j < forages.length; j++) {
+            forages[j]._dbInfo.db = db;
+        }
+    })["catch"](function (err) {
+        _rejectReadiness(dbInfo, err);
+        throw err;
+    });
+}
+
+// FF doesn't like Promises (micro-tasks) and IDDB store operations,
+// so we have to do it with callbacks
+function createTransaction(dbInfo, mode, callback) {
+    try {
+        var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
+        callback(null, tx);
+    } catch (err) {
+        if (!dbInfo.db || err.name === 'InvalidStateError') {
+            return _tryReconnect(dbInfo).then(function () {
+
+                var tx = dbInfo.db.transaction(dbInfo.storeName, mode);
+                callback(null, tx);
+            });
+        }
+
+        callback(err);
+    }
+}
+
 // Open the IndexedDB database (automatically creates one if one didn't
 // previously exist), using any options set in the config.
 function _initStorage(options) {
@@ -484,24 +546,33 @@ function getItem(key, callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-            var req = store.get(key);
-
-            req.onsuccess = function () {
-                var value = req.result;
-                if (value === undefined) {
-                    value = null;
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
-                if (_isEncodedBlob(value)) {
-                    value = _decodeBlob(value);
-                }
-                resolve(value);
-            };
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.get(key);
+
+                    req.onsuccess = function () {
+                        var value = req.result;
+                        if (value === undefined) {
+                            value = null;
+                        }
+                        if (_isEncodedBlob(value)) {
+                            value = _decodeBlob(value);
+                        }
+                        resolve(value);
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -515,35 +586,46 @@ function iterate(iterator, callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-
-            var req = store.openCursor();
-            var iterationNumber = 1;
-
-            req.onsuccess = function () {
-                var cursor = req.result;
-
-                if (cursor) {
-                    var value = cursor.value;
-                    if (_isEncodedBlob(value)) {
-                        value = _decodeBlob(value);
-                    }
-                    var result = iterator(value, cursor.key, iterationNumber++);
-
-                    if (result !== void 0) {
-                        resolve(result);
-                    } else {
-                        cursor["continue"]();
-                    }
-                } else {
-                    resolve();
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
-            };
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.openCursor();
+                    var iterationNumber = 1;
+
+                    req.onsuccess = function () {
+                        var cursor = req.result;
+
+                        if (cursor) {
+                            var value = cursor.value;
+                            if (_isEncodedBlob(value)) {
+                                value = _decodeBlob(value);
+                            }
+                            var result = iterator(value, cursor.key, iterationNumber++);
+
+                            // when the iterator callback retuns any
+                            // (non-`undefined`) value, then we stop
+                            // the iteration immediately
+                            if (result !== void 0) {
+                                resolve(result);
+                            } else {
+                                cursor["continue"]();
+                            }
+                        } else {
+                            resolve();
+                        }
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -575,35 +657,44 @@ function setItem(key, value, callback) {
             }
             return value;
         }).then(function (value) {
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
-            var req = store.put(value, key);
-
-            // The reason we don't _save_ null is because IE 10 does
-            // not support saving the `null` type in IndexedDB. How
-            // ironic, given the bug below!
-            // See: https://github.com/mozilla/localForage/issues/161
-            if (value === null) {
-                value = undefined;
-            }
-
-            transaction.oncomplete = function () {
-                // Cast to undefined so the value passed to
-                // callback/promise is the same as what one would get out
-                // of `getItem()` later. This leads to some weirdness
-                // (setItem('foo', undefined) will return `null`), but
-                // it's not my fault localStorage is our baseline and that
-                // it's weird.
-                if (value === undefined) {
-                    value = null;
+            createTransaction(self._dbInfo, READ_WRITE, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                resolve(value);
-            };
-            transaction.onabort = transaction.onerror = function () {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.put(value, key);
+
+                    // The reason we don't _save_ null is because IE 10 does
+                    // not support saving the `null` type in IndexedDB. How
+                    // ironic, given the bug below!
+                    // See: https://github.com/mozilla/localForage/issues/161
+                    if (value === null) {
+                        value = undefined;
+                    }
+
+                    transaction.oncomplete = function () {
+                        // Cast to undefined so the value passed to
+                        // callback/promise is the same as what one would get out
+                        // of `getItem()` later. This leads to some weirdness
+                        // (setItem('foo', undefined) will return `null`), but
+                        // it's not my fault localStorage is our baseline and that
+                        // it's weird.
+                        if (value === undefined) {
+                            value = null;
+                        }
+
+                        resolve(value);
+                    };
+                    transaction.onabort = transaction.onerror = function () {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -622,30 +713,37 @@ function removeItem(key, callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
+            createTransaction(self._dbInfo, READ_WRITE, function (err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            // We use a Grunt task to make this safe for IE and some
-            // versions of Android (including those used by Cordova).
-            // Normally IE won't like `.delete()` and will insist on
-            // using `['delete']()`, but we have a build step that
-            // fixes this for us now.
-            var req = store["delete"](key);
-            transaction.oncomplete = function () {
-                resolve();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    // We use a Grunt task to make this safe for IE and some
+                    // versions of Android (including those used by Cordova).
+                    // Normally IE won't like `.delete()` and will insist on
+                    // using `['delete']()`, but we have a build step that
+                    // fixes this for us now.
+                    var req = store["delete"](key);
+                    transaction.oncomplete = function () {
+                        resolve();
+                    };
 
-            transaction.onerror = function () {
-                reject(req.error);
-            };
+                    transaction.onerror = function () {
+                        reject(req.error);
+                    };
 
-            // The request will be also be aborted if we've exceeded our storage
-            // space.
-            transaction.onabort = function () {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                    // The request will be also be aborted if we've exceeded our storage
+                    // space.
+                    transaction.onabort = function () {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -658,19 +756,27 @@ function clear(callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var transaction = dbInfo.db.transaction(dbInfo.storeName, 'readwrite');
-            var store = transaction.objectStore(dbInfo.storeName);
-            var req = store.clear();
+            createTransaction(self._dbInfo, READ_WRITE, function (err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            transaction.oncomplete = function () {
-                resolve();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.clear();
 
-            transaction.onabort = transaction.onerror = function () {
-                var err = req.error ? req.error : req.transaction.error;
-                reject(err);
-            };
+                    transaction.oncomplete = function () {
+                        resolve();
+                    };
+
+                    transaction.onabort = transaction.onerror = function () {
+                        var err = req.error ? req.error : req.transaction.error;
+                        reject(err);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -683,17 +789,26 @@ function length(callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-            var req = store.count();
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
+                }
 
-            req.onsuccess = function () {
-                resolve(req.result);
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.count();
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                    req.onsuccess = function () {
+                        resolve(req.result);
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -712,40 +827,49 @@ function key(n, callback) {
         }
 
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-
-            var advanced = false;
-            var req = store.openCursor();
-            req.onsuccess = function () {
-                var cursor = req.result;
-                if (!cursor) {
-                    // this means there weren't enough keys
-                    resolve(null);
-
-                    return;
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                if (n === 0) {
-                    // We have the first key, return it if that's what they
-                    // wanted.
-                    resolve(cursor.key);
-                } else {
-                    if (!advanced) {
-                        // Otherwise, ask the cursor to skip ahead n
-                        // records.
-                        advanced = true;
-                        cursor.advance(n);
-                    } else {
-                        // When we get here, we've got the nth key.
-                        resolve(cursor.key);
-                    }
-                }
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var advanced = false;
+                    var req = store.openCursor();
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                    req.onsuccess = function () {
+                        var cursor = req.result;
+                        if (!cursor) {
+                            // this means there weren't enough keys
+                            resolve(null);
+
+                            return;
+                        }
+
+                        if (n === 0) {
+                            // We have the first key, return it if that's what they
+                            // wanted.
+                            resolve(cursor.key);
+                        } else {
+                            if (!advanced) {
+                                // Otherwise, ask the cursor to skip ahead n
+                                // records.
+                                advanced = true;
+                                cursor.advance(n);
+                            } else {
+                                // When we get here, we've got the nth key.
+                                resolve(cursor.key);
+                            }
+                        }
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
@@ -758,27 +882,35 @@ function keys(callback) {
 
     var promise = new Promise$1(function (resolve, reject) {
         self.ready().then(function () {
-            var dbInfo = self._dbInfo;
-            var store = dbInfo.db.transaction(dbInfo.storeName, 'readonly').objectStore(dbInfo.storeName);
-
-            var req = store.openCursor();
-            var keys = [];
-
-            req.onsuccess = function () {
-                var cursor = req.result;
-
-                if (!cursor) {
-                    resolve(keys);
-                    return;
+            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
+                if (err) {
+                    return reject(err);
                 }
 
-                keys.push(cursor.key);
-                cursor["continue"]();
-            };
+                try {
+                    var store = transaction.objectStore(self._dbInfo.storeName);
+                    var req = store.openCursor();
+                    var keys = [];
 
-            req.onerror = function () {
-                reject(req.error);
-            };
+                    req.onsuccess = function () {
+                        var cursor = req.result;
+
+                        if (!cursor) {
+                            resolve(keys);
+                            return;
+                        }
+
+                        keys.push(cursor.key);
+                        cursor["continue"]();
+                    };
+
+                    req.onerror = function () {
+                        reject(req.error);
+                    };
+                } catch (e) {
+                    reject(e);
+                }
+            });
         })["catch"](reject);
     });
 
diff --git a/dist/localforage.nopromises.min.js b/dist/localforage.nopromises.min.js
index efdd1c3..8d0976f 100644
--- a/dist/localforage.nopromises.min.js
+++ b/dist/localforage.nopromises.min.js
@@ -4,4 +4,4 @@
     https://localforage.github.io/localForage
     (c) 2013-2017 Mozilla, Apache License 2.0
 */
-!function(a){if("object"==typeof exports&&"undefined"!=typeof module)module.exports=a();else if("function"==typeof define&&define.amd)define([],a);else{var b;b="undefined"!=typeof window?window:"undefined"!=typeof global?global:"undefined"!=typeof self?self:this,b.localforage=a()}}(function(){return function a(b,c,d){function e(g,h){if(!c[g]){if(!b[g]){var i="function"==typeof require&&require;if(!h&&i)return i(g,!0);if(f)return f(g,!0);var j=new Error("Cannot find module '"+g+"'");throw j.code="MODULE_NOT_FOUND",j}var k=c[g]={exports:{}};b[g][0].call(k.exports,function(a){var c=b[g][1][a];return e(c||a)},k,k.exports,a,b,c,d)}return c[g].exports}for(var f="function"==typeof require&&require,g=0;g<d.length;g++)e(d[g]);return e}({1:[function(a,b,c){"use strict";function d(a,b){if(!(a instanceof b))throw new TypeError("Cannot call a class as a function")}function e(){try{if("undefined"!=typeof indexedDB)return indexedDB;if("undefined"!=typeof webkitIndexedDB)return 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