diff --git a/lib/appenders/clustered.js b/lib/appenders/clustered.js
index aff720d..0e11d58 100755
--- a/lib/appenders/clustered.js
+++ b/lib/appenders/clustered.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const cluster = require('cluster');
 const log4js = require('../log4js');
 
diff --git a/lib/appenders/dateFile.js b/lib/appenders/dateFile.js
index d673876..fe36cde 100644
--- a/lib/appenders/dateFile.js
+++ b/lib/appenders/dateFile.js
@@ -79,7 +79,7 @@ function shutdown(cb) {
     return cb();
   }
 
-  openFiles.forEach(file => {
+  return openFiles.forEach(file => {
     if (!file.write(eol, 'utf-8')) {
       file.once('drain', () => {
         file.end(complete);
@@ -88,8 +88,6 @@ function shutdown(cb) {
       file.end(complete);
     }
   });
-
-  return cb();
 }
 
 module.exports.appender = appender;
diff --git a/lib/appenders/file.js b/lib/appenders/file.js
index af3127b..b9b82bf 100644
--- a/lib/appenders/file.js
+++ b/lib/appenders/file.js
@@ -115,6 +115,6 @@ function shutdown(cb) {
   });
 }
 
-exports.appender = fileAppender;
-exports.configure = configure;
-exports.shutdown = shutdown;
+module.exports.appender = fileAppender;
+module.exports.configure = configure;
+module.exports.shutdown = shutdown;
diff --git a/lib/appenders/fileSync.js b/lib/appenders/fileSync.js
index bd77720..f942f64 100755
--- a/lib/appenders/fileSync.js
+++ b/lib/appenders/fileSync.js
@@ -192,5 +192,5 @@ function configure(config, options) {
   );
 }
 
-exports.appender = fileAppender;
-exports.configure = configure;
+module.exports.appender = fileAppender;
+module.exports.configure = configure;
diff --git a/lib/appenders/mailgun.js b/lib/appenders/mailgun.js
index 1164318..1f58392 100644
--- a/lib/appenders/mailgun.js
+++ b/lib/appenders/mailgun.js
@@ -1,6 +1,8 @@
 'use strict';
 
 const layouts = require('../layouts');
+const mailgunFactory = require('mailgun-js');
+
 let layout;
 let config;
 let mailgun;
@@ -31,7 +33,7 @@ function configure(_config) {
     layout = layouts.layout(_config.layout.type, _config.layout);
   }
 
-  mailgun = require('mailgun-js')({
+  mailgun = mailgunFactory({
     apiKey: _config.apikey,
     domain: _config.domain
   });
diff --git a/lib/connect-logger.js b/lib/connect-logger.js
index f93652d..0654ed2 100755
--- a/lib/connect-logger.js
+++ b/lib/connect-logger.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const levels = require('./levels');
 const DEFAULT_FORMAT = ':remote-addr - -' +
   ' ":method :url HTTP/:http-version"' +
diff --git a/lib/layouts.js b/lib/layouts.js
index 69c0d8e..2193b15 100644
--- a/lib/layouts.js
+++ b/lib/layouts.js
@@ -4,7 +4,6 @@ const dateFormat = require('./date_format');
 const os = require('os');
 const eol = os.EOL || '\n';
 const util = require('util');
-const semver = require('semver');
 const layoutMakers = {
   messagePassThrough: function () { return messagePassThroughLayout; },
   basic: function () { return basicLayout; },
@@ -31,10 +30,7 @@ function wrapErrorsWithInspect(items) {
     if ((item instanceof Error) && item.stack) {
       return {
         inspect: function () {
-          if (semver.satisfies(process.version, '>=6')) {
-            return util.format(item);
-          }
-          return `${util.format(item)}\n${item.stack}`;
+          return util.format(item);
         }
       };
     }
@@ -82,11 +78,11 @@ function colorize(str, style) {
   return colorizeStart(style) + str + colorizeEnd(style);
 }
 
-function timestampLevelAndCategory(loggingEvent, colour, timezoneOffest) {
+function timestampLevelAndCategory(loggingEvent, colour, timezoneOffset) {
   return colorize(
     formatLogData(
       '[%s] [%s] %s - '
-      , dateFormat.asString(loggingEvent.startTime, timezoneOffest)
+      , dateFormat.asString(loggingEvent.startTime, timezoneOffset)
       , loggingEvent.level
       , loggingEvent.categoryName
     )
diff --git a/lib/log4js.js b/lib/log4js.js
index dfe2395..27390c2 100644
--- a/lib/log4js.js
+++ b/lib/log4js.js
@@ -1,18 +1,5 @@
 /* eslint no-prototype-builtins:1,no-restricted-syntax:[1, "ForInStatement"] */
 'use strict';
-/*
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
 
 /**
  * @fileoverview log4js is a library to log in JavaScript in similar manner
@@ -50,8 +37,11 @@ const layouts = require('./layouts');
 const levels = require('./levels');
 const loggerModule = require('./logger');
 const Logger = loggerModule.Logger;
+const connectLogger = require('./connect-logger').connectLogger;
+
+require('./appenders/console');
+
 const ALL_CATEGORIES = '[all]';
-let appenders = {};
 const loggers = {};
 const appenderMakers = {};
 const appenderShutdowns = {};
@@ -62,12 +52,13 @@ const defaultConfig = {
   replaceConsole: false
 };
 
-require('./appenders/console');
+let appenders = {};
 
 function hasLogger(logger) {
   return loggers.hasOwnProperty(logger);
 }
 
+// todo: this method should be moved back to levels.js, but for loop require, need some refactor
 levels.forName = function (levelStr, levelVal) {
   let level;
   if (typeof levelStr === 'string' && typeof levelVal === 'number') {
@@ -116,7 +107,6 @@ function doesAppenderContainsLogger(appenderCategory, loggerCategory) {
   return normalizedLoggerCategory.substring(0, normalizedAppenderCategory.length) === normalizedAppenderCategory;
 }
 
-
 /**
  * Get a logger instance. Instance is cached on categoryName level.
  * @static
@@ -414,7 +404,7 @@ function loadAppender(appender, appenderModule) {
     throw new Error(`Invalid log4js appender: ${util.inspect(appender)}`);
   }
 
-  module.exports.appenders[appender] = appenderModule.appender.bind(appenderModule);
+  log4js.appenders[appender] = appenderModule.appender.bind(appenderModule);
   if (appenderModule.shutdown) {
     appenderShutdowns[appender] = appenderModule.shutdown.bind(appenderModule);
   }
@@ -463,32 +453,51 @@ function shutdown(cb) {
 }
 
 /**
- *
- * @name Log4js
+ * @name log4js
+ * @namespace Log4js
+ * @property getBufferedLogger
+ * @property getLogger
+ * @property getDefaultLogger
+ * @property hasLogger
+ * @property addAppender
+ * @property loadAppender
+ * @property clearAppenders
+ * @property configure
+ * @property shutdown
+ * @property replaceConsole
+ * @property restoreConsole
+ * @property levels
+ * @property setGlobalLogLevel
+ * @property layouts
+ * @property appenders
+ * @property appenderMakers
+ * @property connectLogger
  */
-module.exports = {
-  getBufferedLogger: getBufferedLogger,
-  getLogger: getLogger,
-  getDefaultLogger: getDefaultLogger,
-  hasLogger: hasLogger,
+const log4js = {
+  getBufferedLogger,
+  getLogger,
+  getDefaultLogger,
+  hasLogger,
 
-  addAppender: addAppender,
-  loadAppender: loadAppender,
-  clearAppenders: clearAppenders,
-  configure: configure,
-  shutdown: shutdown,
+  addAppender,
+  loadAppender,
+  clearAppenders,
+  configure,
+  shutdown,
 
-  replaceConsole: replaceConsole,
-  restoreConsole: restoreConsole,
+  replaceConsole,
+  restoreConsole,
 
-  levels: levels,
-  setGlobalLogLevel: setGlobalLogLevel,
+  levels,
+  setGlobalLogLevel,
 
-  layouts: layouts,
+  layouts,
   appenders: {},
-  appenderMakers: appenderMakers,
-  connectLogger: require('./connect-logger').connectLogger
+  appenderMakers,
+  connectLogger
 };
 
+module.exports = log4js;
+
 // set ourselves up
 configure();
diff --git a/lib/logger.js b/lib/logger.js
index 51b5b10..420726a 100644
--- a/lib/logger.js
+++ b/lib/logger.js
@@ -32,7 +32,7 @@ class LoggingEvent {
 
 /**
  * Logger to log messages.
- * use {@see Log4js.getLogger(String)} to get an instance.
+ * use {@see log4js#getLogger(String)} to get an instance.
  *
  * @name Logger
  * @namespace Log4js