diff --git a/scripts/importTypescript.js b/scripts/importTypescript.js
index 6fa8dba5..6a551da2 100644
--- a/scripts/importTypescript.js
+++ b/scripts/importTypescript.js
@@ -34,7 +34,7 @@ const TYPESCRIPT_LIB_DESTINATION = path.join(__dirname, '../src/lib');
 export const typescriptVersion = "${typeScriptDependencyVersion}";\n`
 	);
 
-	var tsServices = fs
+	let tsServices = fs
 		.readFileSync(path.join(TYPESCRIPT_LIB_SOURCE, 'typescriptServices.js'))
 		.toString();
 
@@ -86,7 +86,7 @@ export const typescriptVersion = "${typeScriptDependencyVersion}";\n`
 		process.exit(1);
 	}
 
-	var tsServices_amd =
+	const tsServices_amd =
 		generatedNote +
 		tsServices +
 		`
@@ -101,7 +101,7 @@ define("vs/language/typescript/lib/typescriptServices", [], function() { return
 		stripSourceMaps(tsServices_amd)
 	);
 
-	var tsServices_esm =
+	const tsServices_esm =
 		generatedNote +
 		tsServices +
 		`
@@ -122,7 +122,7 @@ export var TokenClass = ts.TokenClass;
 		stripSourceMaps(tsServices_esm)
 	);
 
-	var dtsServices = fs
+	let dtsServices = fs
 		.readFileSync(path.join(TYPESCRIPT_LIB_SOURCE, 'typescriptServices.d.ts'))
 		.toString();
 	dtsServices += `
@@ -138,11 +138,11 @@ export = ts;
 
 function importLibs() {
 	function readLibFile(name) {
-		var srcPath = path.join(TYPESCRIPT_LIB_SOURCE, name);
+		const srcPath = path.join(TYPESCRIPT_LIB_SOURCE, name);
 		return fs.readFileSync(srcPath).toString();
 	}
 
-	var strLibResult = `/*---------------------------------------------------------------------------------------------
+	let strLibResult = `/*---------------------------------------------------------------------------------------------
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
@@ -151,7 +151,7 @@ ${generatedNote}
 /** Contains all the lib files */
 export const libFileMap: Record<string, string> = {}
 `;
-	var strIndexResult = `/*---------------------------------------------------------------------------------------------
+	let strIndexResult = `/*---------------------------------------------------------------------------------------------
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
@@ -160,10 +160,10 @@ ${generatedNote}
 /** Contains all the lib files */
 export const libFileSet: Record<string, boolean> = {}
 `;
-	var dtsFiles = fs.readdirSync(TYPESCRIPT_LIB_SOURCE).filter((f) => f.includes('lib.'));
+	const dtsFiles = fs.readdirSync(TYPESCRIPT_LIB_SOURCE).filter((f) => f.includes('lib.'));
 	while (dtsFiles.length > 0) {
-		var name = dtsFiles.shift();
-		var output = readLibFile(name).replace(/\r\n/g, '\n');
+		const name = dtsFiles.shift();
+		const output = readLibFile(name).replace(/\r\n/g, '\n');
 		strLibResult += `libFileMap['${name}'] = "${escapeText(output)}";\n`;
 		strIndexResult += `libFileSet['${name}'] = true;\n`;
 	}
@@ -177,22 +177,23 @@ export const libFileSet: Record<string, boolean> = {}
  */
 function escapeText(text) {
 	// See http://www.javascriptkit.com/jsref/escapesequence.shtml
-	var _backspace = '\b'.charCodeAt(0);
-	var _formFeed = '\f'.charCodeAt(0);
-	var _newLine = '\n'.charCodeAt(0);
-	var _nullChar = 0;
-	var _carriageReturn = '\r'.charCodeAt(0);
-	var _tab = '\t'.charCodeAt(0);
-	var _verticalTab = '\v'.charCodeAt(0);
-	var _backslash = '\\'.charCodeAt(0);
-	var _doubleQuote = '"'.charCodeAt(0);
+	const _backspace = '\b'.charCodeAt(0);
+	const _formFeed = '\f'.charCodeAt(0);
+	const _newLine = '\n'.charCodeAt(0);
+	const _nullChar = 0;
+	const _carriageReturn = '\r'.charCodeAt(0);
+	const _tab = '\t'.charCodeAt(0);
+	const _verticalTab = '\v'.charCodeAt(0);
+	const _backslash = '\\'.charCodeAt(0);
+	const _doubleQuote = '"'.charCodeAt(0);
 
-	var startPos = 0,
-		chrCode,
-		replaceWith = null,
-		resultPieces = [];
+	const len = text.length;
+	let startPos = 0;
+	let chrCode;
+	let replaceWith = null;
+	let resultPieces = [];
 
-	for (var i = 0, len = text.length; i < len; i++) {
+	for (let i = 0; i < len; i++) {
 		chrCode = text.charCodeAt(i);
 		switch (chrCode) {
 			case _backspace:
diff --git a/src/fillers/monaco-editor-core-amd.ts b/src/fillers/monaco-editor-core-amd.ts
index 0e8a7e3f..6af108be 100644
--- a/src/fillers/monaco-editor-core-amd.ts
+++ b/src/fillers/monaco-editor-core-amd.ts
@@ -5,7 +5,7 @@
 
 // Resolves with the global monaco API
 
-declare var define: any;
+declare const define: any;
 
 define([], function () {
 	return (<any>self).monaco;
diff --git a/test/custom-worker.html b/test/custom-worker.html
index f8e32529..4598edaf 100644
--- a/test/custom-worker.html
+++ b/test/custom-worker.html
@@ -26,7 +26,7 @@
 		<button id="getAST">Print AST to console</button>
 
 		<script>
-			var paths = {
+			const paths = {
 				'vs/basic-languages': '../node_modules/monaco-languages/release/dev',
 				'vs/language/typescript/fillers/monaco-editor-core':
 					'../out/amd/fillers/monaco-editor-core-amd',
@@ -41,7 +41,7 @@
 					paths['vs/language/typescript'] = prefix + '/out/amd';
 				}
 			}
-			var require = {
+			self.require = {
 				paths: paths
 			};
 		</script>
diff --git a/test/index.html b/test/index.html
index 4cb3d09c..e28d7459 100644
--- a/test/index.html
+++ b/test/index.html
@@ -18,7 +18,7 @@
 		<button id="updateCompilerSettingsBtn">Update compiler settings</button>
 
 		<script>
-			var paths = {
+			const paths = {
 				'vs/basic-languages': '../node_modules/monaco-languages/release/dev',
 				'vs/language/typescript/fillers/monaco-editor-core':
 					'../out/amd/fillers/monaco-editor-core-amd',
@@ -33,7 +33,7 @@
 					paths['vs/language/typescript'] = prefix + '/out/amd';
 				}
 			}
-			var require = {
+			self.require = {
 				paths: paths
 			};
 		</script>
@@ -178,7 +178,7 @@
 				'vs/basic-languages/monaco.contribution',
 				'vs/language/typescript/monaco.contribution'
 			], () => {
-				var editor = monaco.editor.create(document.getElementById('container'), {
+				const editor = monaco.editor.create(document.getElementById('container'), {
 					value: localStorage.getItem('code') || getDefaultCode(),
 					language: 'typescript',
 					lightbulb: { enabled: true }