Build: Update jsdom; migrate a test with Symbol polyfill to an iframe test

So far, we've been testing that jQuery element iteration works with polyfilled
Symbol & transpiled for-of via a Node test with jsdom with the Symbol global
removed. Unfortunately, jsdom now requires Symbol to be present for its internal
functionality so such a test is no longer possible. Instead, it's been migrated
to an iframe test with transpiled JavaScript.

This PR also enables us to use ECMAScript 2017 or newer in Node.js code.

Closes gh-4305

1 files changed, 12 insertions, 12 deletions

diff --git a/build/tasks/node_smoke_tests.js b/build/tasks/node_smoke_tests.js
index bd0a9150e..e3d69db88 100644
--- a/build/tasks/node_smoke_tests.js
+++ b/build/tasks/node_smoke_tests.js
@@ -1,11 +1,11 @@
-module.exports = function( grunt ) {
+module.exports = ( grunt ) => {
 
 	"use strict";
 
-	var fs = require( "fs" ),
-		spawnTest = require( "./lib/spawn_test.js" ),
-		testsDir = "./test/node_smoke_tests/",
-		nodeSmokeTests = [ "babel:nodeSmokeTests" ];
+	const fs = require( "fs" );
+	const spawnTest = require( "./lib/spawn_test.js" );
+	const testsDir = "./test/node_smoke_tests/";
+	const nodeSmokeTests = [ "babel:nodeSmokeTests" ];
 
 	// Fire up all tests defined in test/node_smoke_tests/*.js in spawned sub-processes.
 	// All the files under test/node_smoke_tests/*.js are supposed to exit with 0 code
@@ -14,15 +14,15 @@ module.exports = function( grunt ) {
 	// each other, e.g. so that they don't share the require cache.
 
 	fs.readdirSync( testsDir )
-		.filter( function( testFilePath ) {
-			return fs.statSync( testsDir + testFilePath ).isFile() &&
-				/\.js$/.test( testFilePath );
-		} )
-		.forEach( function( testFilePath ) {
-			var taskName = "node_" + testFilePath.replace( /\.js$/, "" );
+		.filter( ( testFilePath ) =>
+			fs.statSync( testsDir + testFilePath ).isFile() &&
+				/\.js$/.test( testFilePath )
+		)
+		.forEach( ( testFilePath ) => {
+			const taskName = `node_${ testFilePath.replace( /\.js$/, "" ) }`;
 
 			grunt.registerTask( taskName, function() {
-				spawnTest( this.async(), "node \"test/node_smoke_tests/" + testFilePath + "\"" );
+				spawnTest( this.async(), `node "test/node_smoke_tests/${ testFilePath }"` );
 			} );
 
 			nodeSmokeTests.push( taskName );