diff --git a/.eslintrc b/.eslintrc
index de7f666..2a2f864 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -1,7 +1,7 @@
 {
 	"extends": "airbnb-base",
 	"rules": {
-		"comma-dangle": 1,
+		"comma-dangle": 0,
 		"indent": 2,
 		"object-shorthand": 0,
 		"func-names": 0,
@@ -9,7 +9,9 @@
 		"no-use-before-define": 1,
 		"no-param-reassign": 0,
     "strict": 0,
-    "import/no-extraneous-dependencies": 1
+    "import/no-extraneous-dependencies": 1,
+    "prefer-spread": 0,
+    "prefer-rest-params": 0
 	},
   "parser-options": {
     "ecmaVersion": 6
diff --git a/.gitignore b/.gitignore
index ccfb9e6..d821c0c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,5 @@ test/streams/test-*
 .idea
 .vscode
 .DS_Store
+
+yarn.lock
diff --git a/lib/appenders/categoryFilter.js b/lib/appenders/categoryFilter.js
index 26fc2b9..c4ab9d7 100644
--- a/lib/appenders/categoryFilter.js
+++ b/lib/appenders/categoryFilter.js
@@ -3,8 +3,8 @@
 const log4js = require('../log4js');
 
 function categoryFilter(excludes, appender) {
-  if (typeof(excludes) === 'string') excludes = [excludes];
-  return logEvent => {
+  if (typeof excludes === 'string') excludes = [excludes];
+  return (logEvent) => {
     if (excludes.indexOf(logEvent.categoryName) === -1) {
       appender(logEvent);
     }
diff --git a/lib/appenders/clustered.js b/lib/appenders/clustered.js
index 0e11d58..350209f 100755
--- a/lib/appenders/clustered.js
+++ b/lib/appenders/clustered.js
@@ -1,3 +1,5 @@
+/* eslint-disable no-plusplus */
+
 'use strict';
 
 const cluster = require('cluster');
@@ -70,7 +72,7 @@ function deserializeLoggingEvent(loggingEventString) {
  */
 function createAppender(config) {
   if (cluster.isMaster) {
-    const masterAppender = loggingEvent => {
+    const masterAppender = (loggingEvent) => {
       if (config.actualAppenders) {
         const size = config.actualAppenders.length;
         for (let i = 0; i < size; i++) {
@@ -87,8 +89,8 @@ function createAppender(config) {
     };
 
     // Listen on new workers
-    cluster.on('fork', worker => {
-      worker.on('message', message => {
+    cluster.on('fork', (worker) => {
+      worker.on('message', (message) => {
         if (message.type && message.type === '::log-message') {
           const loggingEvent = deserializeLoggingEvent(message.event);
 
@@ -108,7 +110,7 @@ function createAppender(config) {
     return masterAppender;
   }
 
-  return loggingEvent => {
+  return (loggingEvent) => {
     // If inside the worker process, then send the logger event to master.
     if (cluster.isWorker) {
       // console.log("worker " + cluster.worker.id + " is sending message");
diff --git a/lib/appenders/console.js b/lib/appenders/console.js
index d680a76..6b2e691 100644
--- a/lib/appenders/console.js
+++ b/lib/appenders/console.js
@@ -1,11 +1,12 @@
 'use strict';
 
 const layouts = require('../layouts');
+
 const consoleLog = console.log.bind(console);
 
 function consoleAppender(layout, timezoneOffset) {
   layout = layout || layouts.colouredLayout;
-  return loggingEvent => {
+  return (loggingEvent) => {
     consoleLog(layout(loggingEvent, timezoneOffset));
   };
 }
diff --git a/lib/appenders/dateFile.js b/lib/appenders/dateFile.js
index bfb4bbf..3b31bdc 100644
--- a/lib/appenders/dateFile.js
+++ b/lib/appenders/dateFile.js
@@ -4,12 +4,13 @@ const streams = require('streamroller');
 const layouts = require('../layouts');
 const path = require('path');
 const os = require('os');
+
 const eol = os.EOL || '\n';
 const openFiles = [];
 
 // close open files on process exit.
 process.on('exit', () => {
-  openFiles.forEach(file => {
+  openFiles.forEach((file) => {
     file.end();
   });
 });
@@ -37,7 +38,7 @@ function appender(
   );
   openFiles.push(logFile);
 
-  return logEvent => {
+  return (logEvent) => {
     logFile.write(layout(logEvent, timezoneOffset) + eol, 'utf8');
   };
 }
@@ -69,9 +70,9 @@ function configure(config, options) {
 function shutdown(cb) {
   let completed = 0;
   let error;
-  const complete = err => {
+  const complete = (err) => {
     error = error || err;
-    completed++;
+    completed++; // eslint-disable-line no-plusplus
     if (completed >= openFiles.length) {
       cb(error);
     }
@@ -80,7 +81,7 @@ function shutdown(cb) {
     return cb();
   }
 
-  return openFiles.forEach(file => {
+  return openFiles.forEach((file) => {
     if (!file.write(eol, 'utf-8')) {
       file.once('drain', () => {
         file.end(complete);
diff --git a/lib/appenders/file.js b/lib/appenders/file.js
index ce9be0e..9284e14 100644
--- a/lib/appenders/file.js
+++ b/lib/appenders/file.js
@@ -3,16 +3,16 @@
 const debug = require('debug')('log4js:file');
 const layouts = require('../layouts');
 const path = require('path');
-const fs = require('fs');
 const streams = require('streamroller');
 const os = require('os');
+
 const eol = os.EOL || '\n';
 const openFiles = [];
 
 // close open files on process exit.
 process.on('exit', () => {
   debug('Exit handler called.');
-  openFiles.forEach(file => {
+  openFiles.forEach((file) => {
     file.end();
   });
 });
@@ -20,9 +20,9 @@ process.on('exit', () => {
 // On SIGHUP, close and reopen all files. This allows this appender to work with
 // logrotate. Note that if you are using logrotate, you should not set
 // `logSize`.
-process.on('SIGHUP', function() {
+process.on('SIGHUP', () => {
   debug('SIGHUP handler called.');
-  openFiles.forEach(function(writer) {
+  openFiles.forEach((writer) => {
     writer.closeTheStream(writer.openTheStream.bind(writer));
   });
 });
@@ -40,40 +40,39 @@ process.on('SIGHUP', function() {
  * @param options - options to be passed to the underlying stream
  * @param timezoneOffset - optional timezone offset in minutes (default system local)
  */
-function fileAppender (file, layout, logSize, numBackups, options, timezoneOffset) {
+function fileAppender(file, layout, logSize, numBackups, options, timezoneOffset) {
   file = path.normalize(file);
   layout = layout || layouts.basicLayout;
   numBackups = numBackups === undefined ? 5 : numBackups;
   // there has to be at least one backup if logSize has been specified
   numBackups = numBackups === 0 ? 1 : numBackups;
 
-  debug("Creating file appender (",
-    file, ", ",
-    logSize, ", ",
-    numBackups, ", ",
-    options, ", ",
-    timezoneOffset, ")"
+  debug('Creating file appender (',
+    file, ', ',
+    logSize, ', ',
+    numBackups, ', ',
+    options, ', ',
+    timezoneOffset, ')'
   );
-  var writer = openTheStream(file, logSize, numBackups, options);
+  const writer = openTheStream(file, logSize, numBackups, options);
 
   // push file to the stack of open handlers
   openFiles.push(writer);
 
-  return function(loggingEvent) {
-    writer.write(layout(loggingEvent, timezoneOffset) + eol, "utf8");
+  return function (loggingEvent) {
+    writer.write(layout(loggingEvent, timezoneOffset) + eol, 'utf8');
   };
-
 }
 
 function openTheStream(file, fileSize, numFiles, options) {
-  var stream = new streams.RollingFileStream(
+  const stream = new streams.RollingFileStream(
     file,
     fileSize,
     numFiles,
     options
   );
-  stream.on("error", function (err) {
-    console.error("log4js.fileAppender - Writing to file %s, error happened ", file, err);
+  stream.on('error', (err) => {
+    console.error('log4js.fileAppender - Writing to file %s, error happened ', file, err);
   });
   return stream;
 }
@@ -102,9 +101,9 @@ function configure(config, options) {
 function shutdown(cb) {
   let completed = 0;
   let error;
-  const complete = err => {
+  const complete = (err) => {
     error = error || err;
-    completed++;
+    completed++; // eslint-disable-line no-plusplus
     if (completed >= openFiles.length) {
       cb(error);
     }
@@ -113,7 +112,7 @@ function shutdown(cb) {
     return cb();
   }
 
-  return openFiles.forEach(file => {
+  return openFiles.forEach((file) => {
     if (!file.write(eol, 'utf-8')) {
       file.once('drain', () => {
         file.end(complete);
diff --git a/lib/appenders/fileSync.js b/lib/appenders/fileSync.js
index 8b22909..dab551c 100755
--- a/lib/appenders/fileSync.js
+++ b/lib/appenders/fileSync.js
@@ -5,6 +5,7 @@ const layouts = require('../layouts');
 const path = require('path');
 const fs = require('fs');
 const os = require('os');
+
 const eol = os.EOL || '\n';
 
 class RollingFileSync {
@@ -22,7 +23,7 @@ class RollingFileSync {
     this.filename = filename;
     this.size = size;
     this.backups = backups || 1;
-    this.options = options || { encoding: 'utf8', mode: parseInt('0644', 8), flags: 'a' };
+    this.options = options || { encoding: 'utf8', mode: parseInt('0644', 8), flags: 'a' }; // eslint-disable-line
     this.currentSize = 0;
 
     function currentFileSize(file) {
@@ -149,7 +150,7 @@ function fileAppender(file, layout, logSize, numBackups, timezoneOffset) {
         numFiles
       );
     } else {
-      stream = ((f => {
+      stream = (((f) => {
         // create file if it doesn't exist
         if (!fs.existsSync(f)) {
           fs.appendFileSync(f, '');
@@ -168,7 +169,7 @@ function fileAppender(file, layout, logSize, numBackups, timezoneOffset) {
 
   const logFile = openTheStream(file, logSize, numBackups);
 
-  return loggingEvent => {
+  return (loggingEvent) => {
     logFile.write(layout(loggingEvent, timezoneOffset) + eol);
   };
 }
diff --git a/lib/appenders/gelf.js b/lib/appenders/gelf.js
index 53ec7a4..eb809ed 100644
--- a/lib/appenders/gelf.js
+++ b/lib/appenders/gelf.js
@@ -1,4 +1,5 @@
 'use strict';
+
 const zlib = require('zlib');
 const layouts = require('../layouts');
 const levels = require('../levels');
@@ -41,7 +42,7 @@ let client;
 function gelfAppender(layout, host, port, hostname, facility) {
   let config;
   let customFields;
-  if (typeof(host) === 'object') {
+  if (typeof host === 'object') {
     config = host;
     host = config.host;
     port = config.port;
@@ -76,7 +77,7 @@ function gelfAppender(layout, host, port, hostname, facility) {
    */
   function addCustomFields(loggingEvent, msg) {
     /* append defaultCustomFields firsts */
-    Object.keys(defaultCustomFields).forEach(key => {
+    Object.keys(defaultCustomFields).forEach((key) => {
       // skip _id field for graylog2, skip keys not starts with UNDERSCORE
       if (key.match(/^_/) && key !== '_id') {
         msg[key] = defaultCustomFields[key];
@@ -91,7 +92,7 @@ function gelfAppender(layout, host, port, hostname, facility) {
     if (!firstData.GELF) return; // identify with GELF field defined
     // Remove the GELF key, some gelf supported logging systems drop the message with it
     delete firstData.GELF;
-    Object.keys(firstData).forEach(key => {
+    Object.keys(firstData).forEach((key) => {
       // skip _id field for graylog2, skip keys not starts with UNDERSCORE
       if (key.match(/^_/) || key !== '_id') {
         msg[key] = firstData[key];
@@ -115,20 +116,20 @@ function gelfAppender(layout, host, port, hostname, facility) {
   }
 
   function sendPacket(packet) {
-    client.send(packet, 0, packet.length, port, host, err => {
+    client.send(packet, 0, packet.length, port, host, (err) => {
       if (err) {
         console.error(err);
       }
     });
   }
 
-  return loggingEvent => {
+  return (loggingEvent) => {
     const message = preparePacket(loggingEvent);
     zlib.gzip(new Buffer(JSON.stringify(message)), (err, packet) => {
       if (err) {
         console.error(err.stack);
       } else {
-        if (packet.length > 8192) {
+        if (packet.length > 8192) { // eslint-disable-line
           debug(`Message packet length (${packet.length}) is larger than 8k. Not sending`);
         } else {
           sendPacket(packet);
diff --git a/lib/appenders/hipchat.js b/lib/appenders/hipchat.js
index 4b4e25b..8c3a3be 100644
--- a/lib/appenders/hipchat.js
+++ b/lib/appenders/hipchat.js
@@ -40,7 +40,7 @@ function hipchatAppender(config) {
   const notifier = hipchat.make(config.hipchat_room, config.hipchat_token);
 
   // @lint W074 This function's cyclomatic complexity is too high. (10)
-  return loggingEvent => {
+  return (loggingEvent) => {
     let notifierFn;
 
     notifier.setRoom(config.hipchat_room);
diff --git a/lib/appenders/logFacesAppender.js b/lib/appenders/logFacesAppender.js
index 49cd8e5..ba7bda6 100644
--- a/lib/appenders/logFacesAppender.js
+++ b/lib/appenders/logFacesAppender.js
@@ -1,123 +1,127 @@
 /**
-* logFaces appender sends JSON formatted log events to logFaces receivers.
-* There are two types of receivers supported - raw UDP sockets (for server side apps),
-* and HTTP (for client side apps). Depending on the usage, this appender
-* requires either of the two:
-*
-* For UDP require 'dgram', see 'https://nodejs.org/api/dgram.html'
-* For HTTP require 'axios', see 'https://www.npmjs.com/package/axios'
-*
-* Make sure your project have relevant dependancy installed before using this appender.
-*/
+ * logFaces appender sends JSON formatted log events to logFaces receivers.
+ * There are two types of receivers supported - raw UDP sockets (for server side apps),
+ * and HTTP (for client side apps). Depending on the usage, this appender
+ * requires either of the two:
+ *
+ * For UDP require 'dgram', see 'https://nodejs.org/api/dgram.html'
+ * For HTTP require 'axios', see 'https://www.npmjs.com/package/axios'
+ *
+ * Make sure your project have relevant dependancy installed before using this appender.
+ */
+/* eslint global-require:0 */
 
 'use strict';
 
 const util = require('util');
+
 const context = {};
 
-function datagram(config){
-   const sock = require('dgram').createSocket('udp4');
-   const host = config.remoteHost || '127.0.0.1';
-   const port = config.port || 55201;
+function datagram(config) {
+  const sock = require('dgram').createSocket('udp4');
+  const host = config.remoteHost || '127.0.0.1';
+  const port = config.port || 55201;
 
-   return function(event){
-      const buff = new Buffer(JSON.stringify(event));
-      sock.send(buff, 0, buff.length, port, host, function(err, bytes) {
-         if(err){
-            console.error('log4js.logFacesAppender failed to %s:%d, error: %s',
-                          host, port, err);
-         }
-      });
-   };
+  return function (event) {
+    const buff = new Buffer(JSON.stringify(event));
+    sock.send(buff, 0, buff.length, port, host, (err) => {
+      if (err) {
+        console.error('log4js.logFacesAppender failed to %s:%d, error: %s',
+          host, port, err);
+      }
+    });
+  };
 }
 
-function servlet(config){
-   const axios = require('axios').create();
-   axios.defaults.baseURL = config.url;
-   axios.defaults.timeout = config.timeout || 5000;
-   axios.defaults.headers = {'Content-Type': 'application/json'};
-   axios.defaults.withCredentials = true;
+function servlet(config) {
+  const axios = require('axios').create();
+  axios.defaults.baseURL = config.url;
+  axios.defaults.timeout = config.timeout || 5000;
+  axios.defaults.headers = { 'Content-Type': 'application/json' };
+  axios.defaults.withCredentials = true;
 
-   return function(lfsEvent){
-      axios.post("", lfsEvent)
-      .then(function(response){
-         if(response.status != 200){
-            console.error('log4js.logFacesAppender post to %s failed: %d',
-                           config.url, response.status);
-         }
+  return function (lfsEvent) {
+    axios.post('', lfsEvent)
+      .then((response) => {
+        if (response.status !== 200) {
+          console.error('log4js.logFacesAppender post to %s failed: %d',
+            config.url, response.status);
+        }
       })
-      .catch(function(response){
-         console.error('log4js.logFacesAppender post to %s excepted: %s',
-                          config.url, response.status);
+      .catch((response) => {
+        console.error('log4js.logFacesAppender post to %s excepted: %s',
+          config.url, response.status);
       });
-   };
+  };
 }
 
 /**
-* For UDP (node.js) use the following configuration params:
-*   {
+ * For UDP (node.js) use the following configuration params:
+ *   {
 *      "type": "logFacesAppender",       // must be present for instantiation
 *      "application": "LFS-TEST",        // name of the application (domain)
 *      "remoteHost": "127.0.0.1",        // logFaces server address (hostname)
 *      "port": 55201                     // UDP receiver listening port
 *   }
-*
-* For HTTP (browsers or node.js) use the following configuration params:
-*   {
+ *
+ * For HTTP (browsers or node.js) use the following configuration params:
+ *   {
 *      "type": "logFacesAppender",       // must be present for instantiation
 *      "application": "LFS-TEST",        // name of the application (domain)
 *      "url": "http://lfs-server/logs",  // logFaces receiver servlet URL
 *   }
-*/
+ */
 function logFacesAppender(config) {
-   let send = config.send;
-   if(send === undefined){
-      send = (config.url === undefined) ? datagram(config) : servlet(config);
-   }
+  let send = config.send;
+  if (send === undefined) {
+    send = (config.url === undefined) ? datagram(config) : servlet(config);
+  }
 
-   return function log(event) {
-      // convert to logFaces compact json format
-      const lfsEvent = {
-         a: config.application || '',   // application name
-         t: event.startTime.getTime(),  // time stamp
-         p: event.level.levelStr,       // level (priority)
-         g: event.categoryName,         // logger name
-         m: format(event.data)          // message text
-      };
+  return function log(event) {
+    // convert to logFaces compact json format
+    const lfsEvent = {
+      a: config.application || '',   // application name
+      t: event.startTime.getTime(),  // time stamp
+      p: event.level.levelStr,       // level (priority)
+      g: event.categoryName,         // logger name
+      m: format(event.data)          // message text
+    };
 
-      // add context variables if exist
-      Object.keys(context).forEach(function(key) {
-         lfsEvent[`p_${key}`] = context[key];
-      });
+    // add context variables if exist
+    Object.keys(context).forEach((key) => {
+      lfsEvent[`p_${key}`] = context[key];
+    });
 
-      // send to server
-      send(lfsEvent);
-   };
+    // send to server
+    send(lfsEvent);
+  };
 }
 
 function configure(config) {
-   return logFacesAppender(config);
+  return logFacesAppender(config);
 }
 
-function setContext(key, value){
-   context[key] = value;
+function setContext(key, value) {
+  context[key] = value;
 }
 
 function format(logData) {
   const data = Array.isArray(logData) ?
                logData : Array.prototype.slice.call(arguments);
-  return util.format(...wrapErrorsWithInspect(data));
+  return util.format.apply(util, wrapErrorsWithInspect(data));
 }
 
 function wrapErrorsWithInspect(items) {
-  return items.map(function(item) {
+  return items.map((item) => {
     if ((item instanceof Error) && item.stack) {
-      return { inspect: function() {
+      return {
+        inspect: function () {
           return `${util.format(item)}\n${item.stack}`;
-       }};
-    } else {
-      return item;
+        }
+      };
     }
+
+    return item;
   });
 }
 
diff --git a/lib/appenders/logLevelFilter.js b/lib/appenders/logLevelFilter.js
index 0ce7946..ea0d420 100644
--- a/lib/appenders/logLevelFilter.js
+++ b/lib/appenders/logLevelFilter.js
@@ -6,7 +6,7 @@ const log4js = require('../log4js');
 function logLevelFilter(minLevelString, maxLevelString, appender) {
   const minLevel = levels.toLevel(minLevelString);
   const maxLevel = levels.toLevel(maxLevelString, levels.FATAL);
-  return logEvent => {
+  return (logEvent) => {
     const eventLevel = logEvent.level;
     if (eventLevel.isGreaterThanOrEqualTo(minLevel) && eventLevel.isLessThanOrEqualTo(maxLevel)) {
       appender(logEvent);
diff --git a/lib/appenders/loggly.js b/lib/appenders/loggly.js
index 23af8d7..319ffbe 100644
--- a/lib/appenders/loggly.js
+++ b/lib/appenders/loggly.js
@@ -1,19 +1,23 @@
+/* eslint no-prototype-builtins:1,no-restricted-syntax:[1, "ForInStatement"] */
+
 'use strict';
+
 const layouts = require('../layouts');
 const loggly = require('loggly');
 const os = require('os');
-const passThrough = layouts.messagePassThroughLayout;
 
+const passThrough = layouts.messagePassThroughLayout;
 
 function isAnyObject(value) {
   return value !== null && (typeof value === 'object' || typeof value === 'function');
 }
 
-/* eslint no-prototype-builtins:1,no-restricted-syntax:[1, "ForInStatement"] */
 function numKeys(obj) {
   let res = 0;
   for (const key in obj) {
-    if (obj.hasOwnProperty(key)) res++;
+    if (obj.hasOwnProperty(key)) {
+      res++; // eslint-disable-line no-plusplus
+    }
   }
   return res;
 }
@@ -59,7 +63,7 @@ function logglyAppender(config, layout) {
   const client = loggly.createClient(config);
   if (!layout) layout = passThrough;
 
-  return loggingEvent => {
+  return (loggingEvent) => {
     const result = processTags(loggingEvent.data);
     const deTaggedData = result.deTaggedData;
     const additionalTags = result.additionalTags;
diff --git a/lib/appenders/logstashUDP.js b/lib/appenders/logstashUDP.js
index a1cc3d1..642367c 100644
--- a/lib/appenders/logstashUDP.js
+++ b/lib/appenders/logstashUDP.js
@@ -1,4 +1,5 @@
 'use strict';
+
 const layouts = require('../layouts');
 const dgram = require('dgram');
 const util = require('util');
diff --git a/lib/appenders/mailgun.js b/lib/appenders/mailgun.js
index 1f58392..11341ff 100644
--- a/lib/appenders/mailgun.js
+++ b/lib/appenders/mailgun.js
@@ -11,7 +11,7 @@ function mailgunAppender(_config, _layout) {
   config = _config;
   layout = _layout || layouts.basicLayout;
 
-  return loggingEvent => {
+  return (loggingEvent) => {
     const data = {
       from: _config.from,
       to: _config.to,
diff --git a/lib/appenders/multiprocess.js b/lib/appenders/multiprocess.js
index 62cfb65..3fa8ed5 100644
--- a/lib/appenders/multiprocess.js
+++ b/lib/appenders/multiprocess.js
@@ -2,6 +2,7 @@
 
 const log4js = require('../log4js');
 const net = require('net');
+
 const END_MSG = '__LOG4JS__';
 
 /**
diff --git a/lib/appenders/slack.js b/lib/appenders/slack.js
index cb32665..ae366cd 100644
--- a/lib/appenders/slack.js
+++ b/lib/appenders/slack.js
@@ -2,14 +2,14 @@
 
 const Slack = require('slack-node');
 const layouts = require('../layouts');
-let layout;
 
+let layout;
 let slack;
 
 function slackAppender(_config, _layout) {
   layout = _layout || layouts.basicLayout;
 
-  return loggingEvent => {
+  return (loggingEvent) => {
     const data = {
       channel_id: _config.channel_id,
       text: layout(loggingEvent, _config.timezoneOffset),
diff --git a/lib/appenders/smtp.js b/lib/appenders/smtp.js
index 0a5b39e..dca9a3f 100644
--- a/lib/appenders/smtp.js
+++ b/lib/appenders/smtp.js
@@ -49,7 +49,7 @@ function sendBuffer() {
     if (config.sender) {
       msg.from = config.sender;
     }
-    transport.sendMail(msg, error => {
+    transport.sendMail(msg, (error) => {
       if (error) {
         console.error('log4js.smtpAppender - Error happened', error);
       }
@@ -68,7 +68,7 @@ function getTransportOptions() {
     const transportModule = `nodemailer-${plugin}-transport`;
 
     /* eslint global-require:0 */
-    const transporter = require(transportModule);
+    const transporter = require(transportModule); // eslint-disable-line
     transportOpts = transporter(config.transport.options);
   }
 
@@ -111,8 +111,8 @@ function smtpAppender(_config, _layout) {
 
   shutdownTimeout = ('shutdownTimeout' in config ? config.shutdownTimeout : 5) * 1000;
 
-  return loggingEvent => {
-    unsentCount++;
+  return (loggingEvent) => {
+    unsentCount++;  // eslint-disable-line no-plusplus
     logEventBuffer.push(loggingEvent);
     if (sendInterval > 0) {
       scheduleSend();
diff --git a/lib/appenders/stderr.js b/lib/appenders/stderr.js
index 704e78c..8944468 100644
--- a/lib/appenders/stderr.js
+++ b/lib/appenders/stderr.js
@@ -4,7 +4,7 @@ const layouts = require('../layouts');
 
 function stderrAppender(layout, timezoneOffset) {
   layout = layout || layouts.colouredLayout;
-  return loggingEvent => {
+  return (loggingEvent) => {
     process.stderr.write(`${layout(loggingEvent, timezoneOffset)}\n`);
   };
 }
diff --git a/lib/appenders/stdout.js b/lib/appenders/stdout.js
index 888b916..124ac97 100644
--- a/lib/appenders/stdout.js
+++ b/lib/appenders/stdout.js
@@ -1,16 +1,16 @@
-"use strict";
+'use strict';
 
-var layouts = require('../layouts');
+const layouts = require('../layouts');
 
 function stdoutAppender(layout, timezoneOffset) {
   layout = layout || layouts.colouredLayout;
-  return function(loggingEvent) {
-    process.stdout.write(layout(loggingEvent, timezoneOffset) + '\n');
+  return function (loggingEvent) {
+    process.stdout.write(`${layout(loggingEvent, timezoneOffset)}\n`);
   };
 }
 
 function configure(config) {
-  var layout;
+  let layout;
   if (config.layout) {
     layout = layouts.layout(config.layout.type, config.layout);
   }
diff --git a/lib/connect-logger.js b/lib/connect-logger.js
index abeba12..2c60d3c 100755
--- a/lib/connect-logger.js
+++ b/lib/connect-logger.js
@@ -1,6 +1,9 @@
+/* eslint-disable no-plusplus */
+
 'use strict';
 
 const levels = require('./levels');
+
 const DEFAULT_FORMAT = ':remote-addr - -' +
   ' ":method :url HTTP/:http-version"' +
   ' :status :content-length ":referrer"' +
@@ -120,7 +123,7 @@ function getLogger(logger4js, options) {
  * @return {Array}
  */
 function assembleTokens(req, res, customTokens) {
-  const arrayUniqueTokens = array => {
+  const arrayUniqueTokens = (array) => {
     const a = array.concat();
     for (let i = 0; i < a.length; ++i) {
       for (let j = i + 1; j < a.length; ++j) {
@@ -169,16 +172,16 @@ function assembleTokens(req, res, customTokens) {
     '-'
   });
   defaultTokens.push({
-    token: /:req\[([^\]]+)\]/g,
+    token: /:req\[([^\]]+)]/g,
     replacement: function (_, field) {
       return req.headers[field.toLowerCase()];
     }
   });
   defaultTokens.push({
-    token: /:res\[([^\]]+)\]/g,
+    token: /:res\[([^\]]+)]/g,
     replacement: function (_, field) {
       return res._headers ?
-        (res._headers[field.toLowerCase()] || res.__headers[field])
+             (res._headers[field.toLowerCase()] || res.__headers[field])
         : (res.__headers && res.__headers[field]);
     }
   });
diff --git a/lib/date_format.js b/lib/date_format.js
index 0611adb..8ff1df8 100644
--- a/lib/date_format.js
+++ b/lib/date_format.js
@@ -37,7 +37,7 @@ function offset(timezoneOffset) {
 }
 
 module.exports.asString = function (format, date, timezoneOffset) {
-  if (typeof(format) !== 'string') {
+  if (typeof format !== 'string') {
     timezoneOffset = date;
     date = format;
     format = module.exports.ISO8601_FORMAT;
diff --git a/lib/layouts.js b/lib/layouts.js
index 8e81688..8e04bb1 100644
--- a/lib/layouts.js
+++ b/lib/layouts.js
@@ -2,17 +2,28 @@
 
 const dateFormat = require('./date_format');
 const os = require('os');
-const eol = os.EOL || '\n';
 const util = require('util');
+
+const eol = os.EOL || '\n';
 const layoutMakers = {
-  messagePassThrough: function () { return messagePassThroughLayout; },
-  basic: function () { return basicLayout; },
-  colored: function () { return colouredLayout; },
-  coloured: function () { return colouredLayout; },
+  messagePassThrough: function () {
+    return messagePassThroughLayout;
+  },
+  basic: function () {
+    return basicLayout;
+  },
+  colored: function () {
+    return colouredLayout;
+  },
+  coloured: function () {
+    return colouredLayout;
+  },
   pattern: function (config) {
     return patternLayout(config && config.pattern, config && config.tokens);
   },
-  dummy: function () { return dummyLayout; }
+  dummy: function () {
+    return dummyLayout;
+  }
 };
 const colours = {
   ALL: 'grey',
@@ -27,15 +38,11 @@ const colours = {
 const semver = require('semver');
 
 function wrapErrorsWithInspect(items) {
-  return items.map(item => {
+  return items.map((item) => {
     if ((item instanceof Error) && item.stack) {
       return {
         inspect: function () {
-          if (semver.satisfies(process.version, '>=6')) {
-            return util.format(item);
-          } else {
-            return util.format(item) + '\n' + item.stack;
-          }
+          return semver.satisfies(process.version, '>=6') ? util.format(item) : `${util.format(item)}\n${item.stack}`;
         }
       };
     }
@@ -50,7 +57,7 @@ function formatLogData(logData) {
   if (!Array.isArray(data)) {
     const numArgs = arguments.length;
     data = new Array(numArgs);
-    for (let i = 0; i < numArgs; i++) {
+    for (let i = 0; i < numArgs; i++) { // eslint-disable-line no-plusplus
       data[i] = arguments[i];
     }
   }
@@ -174,7 +181,7 @@ function dummyLayout(loggingEvent) {
  */
 function patternLayout(pattern, tokens, timezoneOffset) {
   const TTCC_CONVERSION_PATTERN = '%r %p %c - %m%n';
-  const regex = /%(-?[0-9]+)?(\.?[0-9]+)?([\[\]cdhmnprzxy%])(\{([^\}]+)\})?|([^%]+)/;
+  const regex = /%(-?[0-9]+)?(\.?[0-9]+)?([[\]cdhmnprzxy%])(\{([^}]+)\})?|([^%]+)/;
 
   pattern = pattern || TTCC_CONVERSION_PATTERN;
 
@@ -259,8 +266,8 @@ function patternLayout(pattern, tokens, timezoneOffset) {
   }
 
   function userDefined(loggingEvent, specifier) {
-    if (typeof(tokens[specifier]) !== 'undefined') {
-      return typeof(tokens[specifier]) === 'function' ? tokens[specifier](loggingEvent) : tokens[specifier];
+    if (typeof tokens[specifier] !== 'undefined') {
+      return typeof tokens[specifier] === 'function' ? tokens[specifier](loggingEvent) : tokens[specifier];
     }
 
     return null;
diff --git a/lib/log4js.js b/lib/log4js.js
index 3b01bd3..e18c62b 100644
--- a/lib/log4js.js
+++ b/lib/log4js.js
@@ -1,4 +1,5 @@
-/* eslint no-prototype-builtins:1,no-restricted-syntax:[1, "ForInStatement"] */
+/* eslint no-prototype-builtins:1,no-restricted-syntax:[1, "ForInStatement"],no-plusplus:0 */
+
 'use strict';
 
 /**
@@ -36,9 +37,10 @@ const util = require('util');
 const layouts = require('./layouts');
 const levels = require('./levels');
 const loggerModule = require('./logger');
-const Logger = loggerModule.Logger;
 const connectLogger = require('./connect-logger').connectLogger;
 
+const Logger = loggerModule.Logger;
+
 require('./appenders/console');
 
 const ALL_CATEGORIES = '[all]';
@@ -81,12 +83,24 @@ function getBufferedLogger(categoryName) {
       delete logger.temp[i];
     }
   };
-  logger.trace = function (message) { logger.temp.push({ level: 'trace', message: message }); };
-  logger.debug = function (message) { logger.temp.push({ level: 'debug', message: message }); };
-  logger.info = function (message) { logger.temp.push({ level: 'info', message: message }); };
-  logger.warn = function (message) { logger.temp.push({ level: 'warn', message: message }); };
-  logger.error = function (message) { logger.temp.push({ level: 'error', message: message }); };
-  logger.fatal = function (message) { logger.temp.push({ level: 'fatal', message: message }); };
+  logger.trace = function (message) {
+    logger.temp.push({ level: 'trace', message: message });
+  };
+  logger.debug = function (message) {
+    logger.temp.push({ level: 'debug', message: message });
+  };
+  logger.info = function (message) {
+    logger.temp.push({ level: 'info', message: message });
+  };
+  logger.warn = function (message) {
+    logger.temp.push({ level: 'warn', message: message });
+  };
+  logger.error = function (message) {
+    logger.temp.push({ level: 'error', message: message });
+  };
+  logger.fatal = function (message) {
+    logger.temp.push({ level: 'fatal', message: message });
+  };
 
   return logger;
 }
@@ -146,14 +160,18 @@ function getLogger(loggerCategoryName) {
     for (const appenderCategory in appenders) {
       if (doesAppenderContainsLogger(appenderCategory, loggerCategoryName)) {
         appenderList = appenders[appenderCategory];
-        appenderList.forEach(appender => { loggers[loggerCategoryName].addListener('log', appender); });
+        appenderList.forEach((appender) => {
+          loggers[loggerCategoryName].addListener('log', appender);
+        });
       }
     }
     /* jshint +W083 */
 
     if (appenders[ALL_CATEGORIES]) {
       appenderList = appenders[ALL_CATEGORIES];
-      appenderList.forEach(appender => { loggers[loggerCategoryName].addListener('log', appender); });
+      appenderList.forEach((appender) => {
+        loggers[loggerCategoryName].addListener('log', appender);
+      });
     }
   }
 
@@ -176,7 +194,7 @@ function addAppender() {
     args = args[0];
   }
 
-  args.forEach(appenderCategory => {
+  args.forEach((appenderCategory) => {
     addAppenderToCategory(appender, appenderCategory);
 
     if (appenderCategory === ALL_CATEGORIES) {
@@ -218,7 +236,7 @@ function clearAppenders() {
 function configureAppenders(appenderList, options) {
   clearAppenders();
   if (appenderList) {
-    appenderList.forEach(appenderConfig => {
+    appenderList.forEach((appenderConfig) => {
       loadAppender(appenderConfig.type);
       let appender;
       appenderConfig.makers = appenderMakers;
@@ -330,13 +348,13 @@ function configure(configurationFileOrObject, options) {
   config = config || process.env.LOG4JS_CONFIG;
   options = options || {};
 
-  if (config === undefined || config === null || typeof(config) === 'string') {
+  if (config === undefined || config === null || typeof config === 'string') {
     if (options.reloadSecs) {
       initReloadConfiguration(config, options);
     }
     config = loadConfigurationFile(config) || defaultConfig;
   } else {
-    if (options.reloadSecs) {
+    if (options.reloadSecs) { // eslint-disable-line
       getLogger('log4js').warn(
         'Ignoring configuration reload parameter for "object" configuration.'
       );
@@ -364,13 +382,15 @@ function replaceConsole(logger) {
 
   logger = logger || getLogger('console');
 
-  ['log', 'debug', 'info', 'warn', 'error'].forEach(item => {
+  ['log', 'debug', 'info', 'warn', 'error'].forEach((item) => {
     console[item] = replaceWith(item === 'log' ? logger.info : logger[item]);
   });
 }
 
 function restoreConsole() {
-  ['log', 'debug', 'info', 'warn', 'error'].forEach(item => { console[item] = originalConsoleFunctions[item]; });
+  ['log', 'debug', 'info', 'warn', 'error'].forEach((item) => {
+    console[item] = originalConsoleFunctions[item];
+  });
 }
 
 /* eslint global-require:0 */
@@ -386,9 +406,9 @@ function restoreConsole() {
 function requireAppender(appender) {
   let appenderModule;
   try {
-    appenderModule = require(`./appenders/${appender}`);
+    appenderModule = require(`./appenders/${appender}`); // eslint-disable-line
   } catch (e) {
-    appenderModule = require(appender);
+    appenderModule = require(appender); // eslint-disable-line
   }
   return appenderModule;
 }
@@ -430,7 +450,7 @@ function shutdown(cb) {
   // not being able to be drained because of run-away log writes.
   loggerModule.disableAllLogWrites();
 
-  //turn off config reloading
+  // turn off config reloading
   if (configState.timerId) {
     clearInterval(configState.timerId);
   }
@@ -458,7 +478,9 @@ function shutdown(cb) {
     return cb();
   }
 
-  shutdownFunctions.forEach(shutdownFct => { shutdownFct(complete); });
+  shutdownFunctions.forEach((shutdownFct) => {
+    shutdownFct(complete);
+  });
 
   return null;
 }
diff --git a/lib/logger.js b/lib/logger.js
index 437b08c..1da0cae 100644
--- a/lib/logger.js
+++ b/lib/logger.js
@@ -1,8 +1,10 @@
 /* eslint no-underscore-dangle:0 */
+
 'use strict';
 
 const levels = require('./levels');
 const EventEmitter = require('events');
+
 const DEFAULT_CATEGORY = '[default]';
 
 let logWritesEnabled = true;
@@ -84,7 +86,7 @@ class Logger extends EventEmitter {
 Logger.DEFAULT_CATEGORY = DEFAULT_CATEGORY;
 Logger.prototype.level = levels.TRACE;
 
-['Trace','Debug','Info','Warn','Error','Fatal', 'Mark'].forEach(addLevelMethods);
+['Trace', 'Debug', 'Info', 'Warn', 'Error', 'Fatal', 'Mark'].forEach(addLevelMethods);
 
 function addLevelMethods(target) {
   const level = levels.toLevel(target);
diff --git a/package.json b/package.json
index 5ffded3..4a14284 100644
--- a/package.json
+++ b/package.json
@@ -38,9 +38,9 @@
   },
   "devDependencies": {
     "conventional-changelog": "^1.1.0",
-    "eslint": "^3.0.0",
-    "eslint-config-airbnb-base": "^4.0.0",
-    "eslint-plugin-import": "^1.5.0",
+    "eslint": "^3.12.0",
+    "eslint-config-airbnb-base": "^11.0.0",
+    "eslint-plugin-import": "^2.0.0",
     "ghooks": "^1.2.1",
     "sandboxed-module": "0.3.0",
     "tape": "^4.6.2",
@@ -51,8 +51,8 @@
     "hipchat-notifier": "^1.1.0",
     "loggly": "^1.1.0",
     "mailgun-js": "^0.7.0",
-    "slack-node": "~0.2.0",
-    "nodemailer": "^2.5.0"
+    "nodemailer": "^2.5.0",
+    "slack-node": "~0.2.0"
   },
   "browser": {
     "os": false