test: change callback function to arrow function

PR-URL: #17699 Reviewed-By: Yosuke Furukawa <yosuke.furukawa@gmail.com> Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Jon Moss <me@jonathanmoss.me> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: skanamaru

test/parallel/test-http-date-header.js

@@ -26,7 +26,7 @@ const http = require('http');
 
 const testResBody = 'other stuff!\n';
 
-const server = http.createServer(function(req, res) {
+const server = http.createServer((req, res) => {
  assert.ok(!('date' in req.headers),
  'Request headers contained a Date.');
  res.writeHead(200, {
@@ -37,16 +37,16 @@ const server = http.createServer(function(req, res) {
 server.listen(0);
 
 
-server.addListener('listening', function() {
+server.addListener('listening', () => {
  const options = {
- port: this.address().port,
+ port: server.address().port,
  path: '/',
  method: 'GET'
  };
- const req = http.request(options, function(res) {
+ const req = http.request(options, (res) => {
  assert.ok('date' in res.headers,
  'Response headers didn\'t contain a Date.');
- res.addListener('end', function() {
+ res.addListener('end', () => {
  server.close();
  process.exit();
  });