diff --git a/Composer/.eslintrc.js b/Composer/.eslintrc.js
index 6ce39182a3..b0e4f3bd7f 100644
--- a/Composer/.eslintrc.js
+++ b/Composer/.eslintrc.js
@@ -52,6 +52,7 @@ module.exports = {
         enforceInMethodNames: true,
       },
     ],
+    'prefer-arrow-callback': 'error',
 
     // plugin: import
     'import/first': 'error',
diff --git a/Composer/packages/electron-server/src/main.ts b/Composer/packages/electron-server/src/main.ts
index 4e71ec2042..79374bb772 100644
--- a/Composer/packages/electron-server/src/main.ts
+++ b/Composer/packages/electron-server/src/main.ts
@@ -145,7 +145,7 @@ async function main() {
 
     mainWindow.show();
 
-    mainWindow.on('closed', function () {
+    mainWindow.on('closed', () => {
       ElectronWindow.destroy();
     });
     log('Rendered application.');
@@ -188,7 +188,7 @@ async function run() {
   });
 
   // Quit when all windows are closed.
-  app.on('window-all-closed', function () {
+  app.on('window-all-closed', () => {
     // On OS X it is common for applications and their menu bar
     // to stay active until the user quits explicitly with Cmd + Q
     if (!isMac()) {
@@ -196,7 +196,7 @@ async function run() {
     }
   });
 
-  app.on('activate', function () {
+  app.on('activate', () => {
     // On OS X it's common to re-create a window in the app when the
     // dock icon is clicked and there are no other windows open.
     if (!ElectronWindow.isBrowserWindowCreated) {
@@ -204,7 +204,7 @@ async function run() {
     }
   });
 
-  app.on('will-finish-launching', function () {
+  app.on('will-finish-launching', () => {
     // Protocol handler for osx
     app.on('open-url', (event, url) => {
       event.preventDefault();
diff --git a/Composer/packages/lib/code-editor/src/LuEditor.tsx b/Composer/packages/lib/code-editor/src/LuEditor.tsx
index a9ca4cd239..6b67877f6c 100644
--- a/Composer/packages/lib/code-editor/src/LuEditor.tsx
+++ b/Composer/packages/lib/code-editor/src/LuEditor.tsx
@@ -98,7 +98,7 @@ const LuEditor: React.FC<LULSPEditorProps> = (props) => {
         if (m) {
           // this is the correct way to combine keycodes in Monaco
           // eslint-disable-next-line no-bitwise
-          editor.addCommand(m.KeyMod.Shift | m.KeyCode.Enter, function () {
+          editor.addCommand(m.KeyMod.Shift | m.KeyCode.Enter, () => {
             const position = editor.getPosition();
             SendRequestWithRetry(languageClient, 'labelingExperienceRequest', { uri, position });
           });
diff --git a/Composer/packages/server/__tests__/models/bot/botProject.test.ts b/Composer/packages/server/__tests__/models/bot/botProject.test.ts
index 05e259590d..f3426c026b 100644
--- a/Composer/packages/server/__tests__/models/bot/botProject.test.ts
+++ b/Composer/packages/server/__tests__/models/bot/botProject.test.ts
@@ -84,7 +84,7 @@ describe('copyTo', () => {
         let files: string[] = [];
         if (fs.existsSync(path)) {
           files = fs.readdirSync(path);
-          files.forEach(function (file) {
+          files.forEach((file) => {
             const curPath = path + '/' + file;
             if (fs.statSync(curPath).isDirectory()) {
               // recurse
diff --git a/Composer/packages/server/src/server.ts b/Composer/packages/server/src/server.ts
index d51af95295..5bf66d2c84 100644
--- a/Composer/packages/server/src/server.ts
+++ b/Composer/packages/server/src/server.ts
@@ -64,7 +64,7 @@ export async function start(pluginDir?: string): Promise<number | string> {
     'upgrade-insecure-requests;',
   ];
 
-  app.all('*', function (req: Request, res: Response, next: NextFunction) {
+  app.all('*', (req: Request, res: Response, next: NextFunction) => {
     res.header('Access-Control-Allow-Origin', '*');
     res.header('Access-Control-Allow-Methods', 'GET,HEAD,OPTIONS,POST,PUT,DELETE');
     res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept, Authorization');
@@ -103,14 +103,14 @@ export async function start(pluginDir?: string): Promise<number | string> {
 
   // next needs to be an arg in order for express to recognize this as the error handler
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
-  app.use(function (err: Error, req: Request, res: Response, _next: NextFunction) {
+  app.use((err: Error, req: Request, res: Response, _next: NextFunction) => {
     if (err) {
       log(err);
       res.status(500).json({ message: err.message });
     }
   });
 
-  app.get('*', function (req, res) {
+  app.get('*', (req, res) => {
     res.render(path.resolve(clientDirectory, 'index.ejs'), { __nonce__: req.__nonce__ });
   });
 
diff --git a/Composer/packages/tools/language-servers/language-generation/__tests__/unitTest/util.test.ts b/Composer/packages/tools/language-servers/language-generation/__tests__/unitTest/util.test.ts
index 2c0ad5aa42..2601bce4cf 100644
--- a/Composer/packages/tools/language-servers/language-generation/__tests__/unitTest/util.test.ts
+++ b/Composer/packages/tools/language-servers/language-generation/__tests__/unitTest/util.test.ts
@@ -4,7 +4,7 @@
 import { textFromTemplate, checkTemplate, updateTemplate } from '../../src/utils';
 
 describe('LG LSP server util function test', () => {
-  it('text from template', function () {
+  it('text from template', () => {
     const template = {
       name: 'Greeting',
       body: '-hi',
@@ -13,7 +13,7 @@ describe('LG LSP server util function test', () => {
     expect(templateText).toContain('# Greeting');
   });
 
-  it('check a valid template', function () {
+  it('check a valid template', () => {
     const template = {
       name: 'Greeting',
       body: '-hi',
@@ -22,7 +22,7 @@ describe('LG LSP server util function test', () => {
     expect(diags).toHaveLength(0);
   });
 
-  it('check an invalid template', function () {
+  it('check an invalid template', () => {
     const template = {
       name: 'Greeting',
       body: 'hi ${ ',
@@ -31,7 +31,7 @@ describe('LG LSP server util function test', () => {
     expect(diags).toHaveLength(1);
   });
 
-  it('update template', function () {
+  it('update template', () => {
     const content = `
 # Greeting
 - hello
diff --git a/Composer/packages/tools/language-servers/language-understanding/__tests__/unitTest/serverUtil.test.ts b/Composer/packages/tools/language-servers/language-understanding/__tests__/unitTest/serverUtil.test.ts
index 20af0d73ce..9c550a7cfd 100644
--- a/Composer/packages/tools/language-servers/language-understanding/__tests__/unitTest/serverUtil.test.ts
+++ b/Composer/packages/tools/language-servers/language-understanding/__tests__/unitTest/serverUtil.test.ts
@@ -12,8 +12,8 @@ const text = `@ml location hasRoles homeaddress
 @ regex zipcode = /[0-9]{5}/
 @ ml mail usesFeature address
 #checktemperature
--it is sunny and the temperature is 
-- the temperature is 35 
+-it is sunny and the temperature is
+- the temperature is 35
 - address is {address=[beijing,100080]}
 `;
 
@@ -37,33 +37,33 @@ const luisObject = {
   prebuiltEntities: [],
 };
 
-describe('LU LSP Server Function Unit Tests', function () {
-  it('Test Get ML Entities', function () {
+describe('LU LSP Server Function Unit Tests', () => {
+  it('Test Get ML Entities', () => {
     const result = util.getMLEntities(text);
     assert.deepStrictEqual(result, ['location', 'mail']);
   });
 
-  it('Test Get Composites Entities', function () {
+  it('Test Get Composites Entities', () => {
     const result = util.getCompositesEntities(luisObject);
     assert.deepStrictEqual(result, ['geoInfo']);
   });
 
-  it('Test Get RegExp Entities', function () {
+  it('Test Get RegExp Entities', () => {
     const result = util.getRegexEntities(luisObject);
     assert.deepStrictEqual(result, ['zipcode']);
   });
 
-  it('Test Get All Parsed Entities', function () {
+  it('Test Get All Parsed Entities', () => {
     const result = util.getSuggestionEntities(luisObject, util.suggestionAllEntityTypes);
     assert.deepStrictEqual(result, ['address', 'zipcode', 'city', 'geoInfo']);
   });
 
-  it('Test Get All Parsed Roles', function () {
+  it('Test Get All Parsed Roles', () => {
     const result = util.getSuggestionRoles(luisObject, util.suggestionAllEntityTypes);
     assert.deepStrictEqual(result, ['role1', 'role2']);
   });
 
-  it('Test Entity Can UsesFeature', function () {
+  it('Test Entity Can UsesFeature', () => {
     let lineContent = '@ geoInfo usesFeature ';
     let result = util.matchedEntityCanUsesFeature(lineContent, text, luisObject);
     assert.equal(result, true);
@@ -81,7 +81,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Intent Can UsesFeature', function () {
+  it('Test Intent Can UsesFeature', () => {
     let text = '@ intent mockIntent usesFeature ';
     let result = util.matchIntentUsesFeatures(text);
     assert.equal(result, true);
@@ -91,7 +91,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Intent In a Entity Definiton', function () {
+  it('Test Intent In a Entity Definiton', () => {
     let text = '@ intent mockIntent';
     let result = util.matchIntentInEntityDef(text);
     assert.equal(result, true);
@@ -101,7 +101,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Entity Definition', function () {
+  it('Test Entity Definition', () => {
     let text = '@ ';
     let result = util.isEntityType(text);
     assert.equal(result, true);
@@ -111,7 +111,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Prebuilt Entity Definition', function () {
+  it('Test Prebuilt Entity Definition', () => {
     let text = '@ prebuilt ';
     let result = util.isPrebuiltEntity(text);
     assert.equal(result, true);
@@ -121,7 +121,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test RegExp Entity Definition', function () {
+  it('Test RegExp Entity Definition', () => {
     let text = '@ regex zipcode =';
     let result = util.isRegexEntity(text);
     assert.equal(result, true);
@@ -131,7 +131,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Seperated Line Entity', function () {
+  it('Test Seperated Line Entity', () => {
     let text = '@ zipcode =';
     let result = util.isSeperatedEntityDef(text);
     assert.equal(result, true);
@@ -141,7 +141,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Entity Name ', function () {
+  it('Test Entity Name ', () => {
     let text = '@ ml location';
     let result = util.isEntityName(text);
     assert.equal(result, true);
@@ -155,7 +155,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Composite Entity ', function () {
+  it('Test Composite Entity ', () => {
     let text = '@ composite location = [';
     let result = util.isCompositeEntity(text);
     assert.equal(result, true);
@@ -169,7 +169,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Entering Pattern ', function () {
+  it('Test Entering Pattern ', () => {
     let text = '- The weather in Seattle is { ';
     let result = util.matchedEnterPattern(text);
     assert.equal(result, true);
@@ -183,7 +183,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Entering Roles ', function () {
+  it('Test Entering Roles ', () => {
     let text = '- The weather in Seattle is {morning: ';
     let result = util.matchedRolesPattern(text);
     assert.equal(result, true);
@@ -197,7 +197,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Entering Entity ', function () {
+  it('Test Entering Entity ', () => {
     let text = '- The weather in Seattle is {@ ';
     let result = util.matchedEntityPattern(text);
     assert.equal(result, true);
@@ -211,7 +211,7 @@ describe('LU LSP Server Function Unit Tests', function () {
     assert.equal(result, false);
   });
 
-  it('Test Remove Labeled Utterance', function () {
+  it('Test Remove Labeled Utterance', () => {
     let text = '- this is a {type = Audio} message from {device = PC}';
     let result = util.removeLabelsInUtterance(text);
     assert.equal(result, '- this is a Audio message from PC');