diff --git a/lib/NullFactory.js b/lib/NullFactory.js
index d3b2e32dc33..90ede1fe3f1 100644
--- a/lib/NullFactory.js
+++ b/lib/NullFactory.js
@@ -2,9 +2,11 @@
 	MIT License http://www.opensource.org/licenses/mit-license.php
 	Author Tobias Koppers @sokra
 */
-function NullFactory() {}
-module.exports = NullFactory;
+"use strict";
 
-NullFactory.prototype.create = function(data, callback) {
-	return callback();
-};
+class NullFactory {
+	create(data, callback) {
+		return callback();
+	}
+}
+module.exports = NullFactory;
diff --git a/lib/OptionsApply.js b/lib/OptionsApply.js
index 016c9f77841..3b1ec316485 100644
--- a/lib/OptionsApply.js
+++ b/lib/OptionsApply.js
@@ -2,9 +2,9 @@
 	MIT License http://www.opensource.org/licenses/mit-license.php
 	Author Tobias Koppers @sokra
 */
-function OptionsApply() {}
-module.exports = OptionsApply;
-
-OptionsApply.prototype.process = function(options, compiler) {
+"use strict";
 
-};
+class OptionsApply {
+	process(options, compiler) {}
+}
+module.exports = OptionsApply;
diff --git a/lib/ProgressPlugin.js b/lib/ProgressPlugin.js
index 5fbda81649d..9059c0767f6 100644
--- a/lib/ProgressPlugin.js
+++ b/lib/ProgressPlugin.js
@@ -2,188 +2,189 @@
 	MIT License http://www.opensource.org/licenses/mit-license.php
 	Author Tobias Koppers @sokra
 */
-function ProgressPlugin(options) {
-	if(typeof options === "function") {
-		options = {
-			handler: options
-		};
+"use strict";
+
+class ProgressPlugin {
+
+	constructor(options) {
+		if(typeof options === "function") {
+			options = {
+				handler: options
+			};
+		}
+		options = options || {};
+		this.profile = options.profile;
+		this.handler = options.handler;
 	}
-	options = options || {};
-	this.profile = options.profile;
-	this.handler = options.handler;
-}
-module.exports = ProgressPlugin;
 
-ProgressPlugin.prototype.apply = function(compiler) {
-	var handler = this.handler || defaultHandler;
-	var profile = this.profile;
-	if(compiler.compilers) {
-		var states = new Array(compiler.compilers.length);
-		compiler.compilers.forEach(function(compiler, idx) {
-			compiler.apply(new ProgressPlugin(function(p, msg) {
-				states[idx] = Array.prototype.slice.apply(arguments);
-				handler.apply(null, [
-					states.map(function(state) {
-						return state && state[0] || 0;
-					}).reduce(function(a, b) {
-						return a + b;
-					}) / states.length,
-					"[" + idx + "] " + msg
-				].concat(Array.prototype.slice.call(arguments, 2)));
-			}));
-		});
-	} else {
-		var lastModulesCount = 0;
-		var moduleCount = 500;
-		var doneModules = 0;
-		var activeModules = [];
+	apply(compiler) {
+		const handler = this.handler || defaultHandler;
+		const profile = this.profile;
+		if(compiler.compilers) {
+			const states = new Array(compiler.compilers.length);
+			compiler.compilers.forEach(function(compiler, idx) {
+				compiler.apply(new ProgressPlugin((p, msg) => {
+					states[idx] = Array.prototype.slice.apply(arguments);
+					handler.apply(null, [
+						states.map(state => state && state[0] || 0).reduce((a, b) => a + b) / states.length,
+						`[${idx}] ${msg}`
+					].concat(Array.prototype.slice.call(arguments, 2)));
+				}));
+			});
+		} else {
+			let lastModulesCount = 0;
+			let moduleCount = 500;
+			let doneModules = 0;
+			const activeModules = [];
 
-		var update = function update(module) {
-			handler(
-				0.1 + (doneModules / Math.max(lastModulesCount, moduleCount)) * 0.6,
-				"building modules",
-				doneModules + "/" + moduleCount + " modules",
-				activeModules.length + " active",
-				activeModules[activeModules.length - 1]
-			);
-		};
+			const update = function update(module) {
+				handler(
+					0.1 + (doneModules / Math.max(lastModulesCount, moduleCount)) * 0.6,
+					"building modules",
+					`${doneModules}/${moduleCount} modules`,
+					`${activeModules.length} active`,
+					activeModules[activeModules.length - 1]
+				);
+			};
 
-		var moduleDone = function moduleDone(module) {
-			doneModules++;
-			var ident = module.identifier();
-			if(ident) {
-				var idx = activeModules.indexOf(ident);
-				if(idx >= 0) activeModules.splice(idx, 1);
-			}
-			update();
-		};
-		compiler.plugin("compilation", function(compilation) {
-			if(compilation.compiler.isChild()) return;
-			lastModulesCount = moduleCount;
-			moduleCount = 0;
-			doneModules = 0;
-			handler(0, "compiling");
-			compilation.plugin("build-module", function(module) {
-				moduleCount++;
-				var ident = module.identifier();
+			const moduleDone = function moduleDone(module) {
+				doneModules++;
+				const ident = module.identifier();
 				if(ident) {
-					activeModules.push(ident);
+					const idx = activeModules.indexOf(ident);
+					if(idx >= 0) activeModules.splice(idx, 1);
 				}
 				update();
-			});
-			compilation.plugin("failed-module", moduleDone);
-			compilation.plugin("succeed-module", moduleDone);
-			var syncHooks = {
-				"seal": [0.71, "sealing"],
-				"optimize": [0.72, "optimizing"],
-				"optimize-modules-basic": [0.73, "basic module optimization"],
-				"optimize-modules": [0.74, "module optimization"],
-				"optimize-modules-advanced": [0.75, "advanced module optimization"],
-				"optimize-chunks-basic": [0.76, "basic chunk optimization"],
-				"optimize-chunks": [0.77, "chunk optimization"],
-				"optimize-chunks-advanced": [0.78, "advanced chunk optimization"],
-				// optimize-tree
-				"revive-modules": [0.80, "module reviving"],
-				"optimize-module-order": [0.81, "module order optimization"],
-				"optimize-module-ids": [0.82, "module id optimization"],
-				"revive-chunks": [0.83, "chunk reviving"],
-				"optimize-chunk-order": [0.84, "chunk order optimization"],
-				"optimize-chunk-ids": [0.85, "chunk id optimization"],
-				"before-hash": [0.86, "hashing"],
-				"before-module-assets": [0.87, "module assets processing"],
-				"before-chunk-assets": [0.88, "chunk assets processing"],
-				"additional-chunk-assets": [0.89, "additional chunk assets processing"],
-				"record": [0.90, "recording"]
 			};
-			Object.keys(syncHooks).forEach(function(name) {
-				var pass = 0;
-				var settings = syncHooks[name];
-				compilation.plugin(name, function() {
-					if(pass++ > 0)
-						handler(settings[0], settings[1], "pass " + pass);
-					else
-						handler(settings[0], settings[1]);
+			compiler.plugin("compilation", function(compilation) {
+				if(compilation.compiler.isChild()) return;
+				lastModulesCount = moduleCount;
+				moduleCount = 0;
+				doneModules = 0;
+				handler(0, "compiling");
+				compilation.plugin("build-module", function(module) {
+					moduleCount++;
+					const ident = module.identifier();
+					if(ident) {
+						activeModules.push(ident);
+					}
+					update();
+				});
+				compilation.plugin("failed-module", moduleDone);
+				compilation.plugin("succeed-module", moduleDone);
+				const syncHooks = {
+					"seal": [0.71, "sealing"],
+					"optimize": [0.72, "optimizing"],
+					"optimize-modules-basic": [0.73, "basic module optimization"],
+					"optimize-modules": [0.74, "module optimization"],
+					"optimize-modules-advanced": [0.75, "advanced module optimization"],
+					"optimize-chunks-basic": [0.76, "basic chunk optimization"],
+					"optimize-chunks": [0.77, "chunk optimization"],
+					"optimize-chunks-advanced": [0.78, "advanced chunk optimization"],
+					// optimize-tree
+					"revive-modules": [0.80, "module reviving"],
+					"optimize-module-order": [0.81, "module order optimization"],
+					"optimize-module-ids": [0.82, "module id optimization"],
+					"revive-chunks": [0.83, "chunk reviving"],
+					"optimize-chunk-order": [0.84, "chunk order optimization"],
+					"optimize-chunk-ids": [0.85, "chunk id optimization"],
+					"before-hash": [0.86, "hashing"],
+					"before-module-assets": [0.87, "module assets processing"],
+					"before-chunk-assets": [0.88, "chunk assets processing"],
+					"additional-chunk-assets": [0.89, "additional chunk assets processing"],
+					"record": [0.90, "recording"]
+				};
+				Object.keys(syncHooks).forEach(name => {
+					let pass = 0;
+					const settings = syncHooks[name];
+					compilation.plugin(name, () => {
+						if(pass++ > 0)
+							handler(settings[0], settings[1], `pass ${pass}`);
+						else
+							handler(settings[0], settings[1]);
+					});
+				});
+				compilation.plugin("optimize-tree", (chunks, modules, callback) => {
+					handler(0.79, "module and chunk tree optimization");
+					callback();
+				});
+				compilation.plugin("additional-assets", callback => {
+					handler(0.91, "additional asset processing");
+					callback();
+				});
+				compilation.plugin("optimize-chunk-assets", (chunks, callback) => {
+					handler(0.92, "chunk asset optimization");
+					callback();
+				});
+				compilation.plugin("optimize-assets", (assets, callback) => {
+					handler(0.94, "asset optimization");
+					callback();
 				});
 			});
-			compilation.plugin("optimize-tree", function(chunks, modules, callback) {
-				handler(0.79, "module and chunk tree optimization");
-				callback();
-			});
-			compilation.plugin("additional-assets", function(callback) {
-				handler(0.91, "additional asset processing");
-				callback();
-			});
-			compilation.plugin("optimize-chunk-assets", function(chunks, callback) {
-				handler(0.92, "chunk asset optimization");
+			compiler.plugin("emit", (compilation, callback) => {
+				handler(0.95, "emitting");
 				callback();
 			});
-			compilation.plugin("optimize-assets", function(assets, callback) {
-				handler(0.94, "asset optimization");
-				callback();
+			compiler.plugin("done", () => {
+				handler(1, "");
 			});
-		});
-		compiler.plugin("emit", function(compilation, callback) {
-			handler(0.95, "emitting");
-			callback();
-		});
-		compiler.plugin("done", function() {
-			handler(1, "");
-		});
-	}
+		}
 
-	var lineCaretPosition = 0,
-		lastState, lastStateTime;
+		let lineCaretPosition = 0,
+			lastState, lastStateTime;
 
-	function defaultHandler(percentage, msg) {
-		var state = msg;
-		var details = Array.prototype.slice.call(arguments, 2);
-		if(percentage < 1) {
-			percentage = Math.floor(percentage * 100);
-			msg = percentage + "% " + msg;
-			if(percentage < 100) {
-				msg = " " + msg;
-			}
-			if(percentage < 10) {
-				msg = " " + msg;
-			}
-			details.forEach(function(detail) {
-				if(!detail) return;
-				if(detail.length > 40) {
-					detail = "..." + detail.substr(detail.length - 37);
+		function defaultHandler(percentage, msg) {
+			let state = msg;
+			const details = Array.prototype.slice.call(arguments, 2);
+			if(percentage < 1) {
+				percentage = Math.floor(percentage * 100);
+				msg = `${percentage}% ${msg}`;
+				if(percentage < 100) {
+					msg = ` ${msg}`;
 				}
-				msg += " " + detail;
-			});
-		}
-		if(profile) {
-			state = state.replace(/^\d+\/\d+\s+/, "");
-			if(percentage === 0) {
-				lastState = null;
-				lastStateTime = +new Date();
-			} else if(state !== lastState || percentage === 1) {
-				var now = +new Date();
-				if(lastState) {
-					var stateMsg = (now - lastStateTime) + "ms " + lastState;
-					goToLineStart(stateMsg);
-					process.stderr.write(stateMsg + "\n");
-					lineCaretPosition = 0;
+				if(percentage < 10) {
+					msg = ` ${msg}`;
 				}
-				lastState = state;
-				lastStateTime = now;
+				details.forEach(detail => {
+					if(!detail) return;
+					if(detail.length > 40) {
+						detail = `...${detail.substr(detail.length - 37)}`;
+					}
+					msg += ` ${detail}`;
+				});
 			}
+			if(profile) {
+				state = state.replace(/^\d+\/\d+\s+/, "");
+				if(percentage === 0) {
+					lastState = null;
+					lastStateTime = +new Date();
+				} else if(state !== lastState || percentage === 1) {
+					const now = +new Date();
+					if(lastState) {
+						const stateMsg = `${now - lastStateTime}ms ${lastState}`;
+						goToLineStart(stateMsg);
+						process.stderr.write(stateMsg + "\n");
+						lineCaretPosition = 0;
+					}
+					lastState = state;
+					lastStateTime = now;
+				}
+			}
+			goToLineStart(msg);
+			process.stderr.write(msg);
 		}
-		goToLineStart(msg);
-		process.stderr.write(msg);
-	}
 
-	function goToLineStart(nextMessage) {
-		var str = "";
-		for(; lineCaretPosition > nextMessage.length; lineCaretPosition--) {
-			str += "\b \b";
-		}
-		for(var i = 0; i < lineCaretPosition; i++) {
-			str += "\b";
+		function goToLineStart(nextMessage) {
+			let str = "";
+			for(; lineCaretPosition > nextMessage.length; lineCaretPosition--) {
+				str += "\b \b";
+			}
+			for(var i = 0; i < lineCaretPosition; i++) {
+				str += "\b";
+			}
+			lineCaretPosition = nextMessage.length;
+			if(str) process.stderr.write(str);
 		}
-		lineCaretPosition = nextMessage.length;
-		if(str) process.stderr.write(str);
 	}
-};
+}
+module.exports = ProgressPlugin;
diff --git a/lib/ProvidePlugin.js b/lib/ProvidePlugin.js
index 403189a2d48..fdcfaf48a96 100644
--- a/lib/ProvidePlugin.js
+++ b/lib/ProvidePlugin.js
@@ -2,51 +2,54 @@
 	MIT License http://www.opensource.org/licenses/mit-license.php
 	Author Tobias Koppers @sokra
 */
-var ParserHelpers = require("./ParserHelpers");
-var ConstDependency = require("./dependencies/ConstDependency");
+"use strict";
 
-var NullFactory = require("./NullFactory");
+const ParserHelpers = require("./ParserHelpers");
+const ConstDependency = require("./dependencies/ConstDependency");
 
-function ProvidePlugin(definitions) {
-	this.definitions = definitions;
-}
-module.exports = ProvidePlugin;
-ProvidePlugin.prototype.apply = function(compiler) {
-	var definitions = this.definitions;
-	compiler.plugin("compilation", function(compilation, params) {
-		compilation.dependencyFactories.set(ConstDependency, new NullFactory());
-		compilation.dependencyTemplates.set(ConstDependency, new ConstDependency.Template());
-		params.normalModuleFactory.plugin("parser", function(parser, parserOptions) {
-			Object.keys(definitions).forEach(function(name) {
-				var request = [].concat(definitions[name]);
-				var splittedName = name.split(".");
-				if(splittedName.length > 0) {
-					splittedName.slice(1).forEach(function(_, i) {
-						var name = splittedName.slice(0, i + 1).join(".");
-						parser.plugin("can-rename " + name, ParserHelpers.approve);
-					});
-				}
-				parser.plugin("expression " + name, function(expr) {
-					var nameIdentifier = name;
-					var scopedName = name.indexOf(".") >= 0;
-					var expression = "require(" + JSON.stringify(request[0]) + ")";
-					if(scopedName) {
-						nameIdentifier = "__webpack_provided_" + name.replace(/\./g, "_dot_");
-					}
-					if(request.length > 1) {
-						expression += request.slice(1).map(function(r) {
-							return "[" + JSON.stringify(r) + "]";
-						}).join("");
-					}
-					if(!ParserHelpers.addParsedVariableToModule(this, nameIdentifier, expression)) {
-						return false;
-					}
-					if(scopedName) {
-						ParserHelpers.toConstantDependency(nameIdentifier).bind(this)(expr);
+const NullFactory = require("./NullFactory");
+
+class ProvidePlugin {
+	constructor(definitions) {
+		this.definitions = definitions;
+	}
+
+	apply(compiler) {
+		const definitions = this.definitions;
+		compiler.plugin("compilation", (compilation, params) => {
+			compilation.dependencyFactories.set(ConstDependency, new NullFactory());
+			compilation.dependencyTemplates.set(ConstDependency, new ConstDependency.Template());
+			params.normalModuleFactory.plugin("parser", (parser, parserOptions) => {
+				Object.keys(definitions).forEach(name => {
+					var request = [].concat(definitions[name]);
+					var splittedName = name.split(".");
+					if(splittedName.length > 0) {
+						splittedName.slice(1).forEach((_, i) => {
+							const name = splittedName.slice(0, i + 1).join(".");
+							parser.plugin(`can-rename ${name}`, ParserHelpers.approve);
+						});
 					}
-					return true;
+					parser.plugin(`expression ${name}`, function(expr) {
+						let nameIdentifier = name;
+						const scopedName = name.indexOf(".") >= 0;
+						let expression = `require(${JSON.stringify(request[0])})`;
+						if(scopedName) {
+							nameIdentifier = `__webpack_provided_${name.replace(/\./g, "_dot_")}`;
+						}
+						if(request.length > 1) {
+							expression += request.slice(1).map(r => `[${JSON.stringify(r)}]`).join("");
+						}
+						if(!ParserHelpers.addParsedVariableToModule(this, nameIdentifier, expression)) {
+							return false;
+						}
+						if(scopedName) {
+							ParserHelpers.toConstantDependency(nameIdentifier).bind(this)(expr);
+						}
+						return true;
+					});
 				});
 			});
 		});
-	});
-};
+	}
+}
+module.exports = ProvidePlugin;