Improve legacy iterators check

Author: mhassan1

polyfills/Array/prototype/values/polyfill.js

@@ -1,16 +1,16 @@
 /* global CreateMethodProperty, Symbol, ToObject, ArrayIterator */
 // 22.1.3.30/ Array.prototype.values ( )
 
-var hasLegacyIterator = !(function () {
+var hasModernIterator = function () {
 	// firefox 44 and below uses legacy iterators
 	// https://github.com/zloirock/core-js/commit/bb3b34bbf92b1d1a7b50d3a5a445c84dc2fb5cd5#diff-25d2a16dc5a355ce40a572773be144d1c8e085a809633e42ec$
 	var IteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbol.iterator]()));
 	var test = {};
 	return IteratorPrototype[Symbol.iterator].call(test) === test;
-})();
+}
 
 // Firefox, Chrome and Opera have Array.prototype[Symbol.iterator], which is the exact same function as Array.prototype.values.
-if ('Symbol' in self && 'iterator' in Symbol && typeof Array.prototype[Symbol.iterator] === 'function' && !hasLegacyIterator) {
+if ('Symbol' in self && 'iterator' in Symbol && typeof Array.prototype[Symbol.iterator] === 'function' && hasModernIterator()) {
 	CreateMethodProperty(Array.prototype, 'values', Array.prototype[Symbol.iterator]);
 } else {
 	CreateMethodProperty(Array.prototype, 'values', function values () {