1 var $ = require('../internals/export');
2 var getBuiltIn = require('../internals/get-built-in');
3 var apply = require('../internals/function-apply');
4 var bind = require('../internals/function-bind');
5 var aConstructor = require('../internals/a-constructor');
6 var anObject = require('../internals/an-object');
7 var isObject = require('../internals/is-object');
8 var create = require('../internals/object-create');
9 var fails = require('../internals/fails');
11 var nativeConstruct = getBuiltIn('Reflect', 'construct');
12 var ObjectPrototype = Object.prototype;
15 // `Reflect.construct` method
16 // https://tc39.es/ecma262/#sec-reflect.construct
17 // MS Edge supports only 2 arguments and argumentsList argument is optional
18 // FF Nightly sets third argument as `new.target`, but does not create `this` from it
19 var NEW_TARGET_BUG = fails(function () {
20 function F() { /* empty */ }
21 return !(nativeConstruct(function () { /* empty */ }, [], F) instanceof F);
24 var ARGS_BUG = !fails(function () {
25 nativeConstruct(function () { /* empty */ });
28 var FORCED = NEW_TARGET_BUG || ARGS_BUG;
30 $({ target: 'Reflect', stat: true, forced: FORCED, sham: FORCED }, {
31 construct: function construct(Target, args /* , newTarget */) {
34 var newTarget = arguments.length < 3 ? Target : aConstructor(arguments[2]);
35 if (ARGS_BUG && !NEW_TARGET_BUG) return nativeConstruct(Target, args, newTarget);
36 if (Target == newTarget) {
37 // w/o altered newTarget, optimization for 0-4 arguments
38 switch (args.length) {
39 case 0: return new Target();
40 case 1: return new Target(args[0]);
41 case 2: return new Target(args[0], args[1]);
42 case 3: return new Target(args[0], args[1], args[2]);
43 case 4: return new Target(args[0], args[1], args[2], args[3]);
45 // w/o altered newTarget, lot of arguments case
47 apply(push, $args, args);
48 return new (apply(bind, Target, $args))();
50 // with altered newTarget, not support built-in constructors
51 var proto = newTarget.prototype;
52 var instance = create(isObject(proto) ? proto : ObjectPrototype);
53 var result = apply(Target, instance, args);
54 return isObject(result) ? result : instance;