| var $ = require('../internals/export'); |
| var getBuiltIn = require('../internals/get-built-in'); |
| var aFunction = require('../internals/a-function'); |
| var anObject = require('../internals/an-object'); |
| var isObject = require('../internals/is-object'); |
| var create = require('../internals/object-create'); |
| var bind = require('../internals/function-bind'); |
| var fails = require('../internals/fails'); |
| |
| var nativeConstruct = getBuiltIn('Reflect', 'construct'); |
| |
| // `Reflect.construct` method |
| // https://tc39.github.io/ecma262/#sec-reflect.construct |
| // MS Edge supports only 2 arguments and argumentsList argument is optional |
| // FF Nightly sets third argument as `new.target`, but does not create `this` from it |
| var NEW_TARGET_BUG = fails(function () { |
| function F() { /* empty */ } |
| return !(nativeConstruct(function () { /* empty */ }, [], F) instanceof F); |
| }); |
| var ARGS_BUG = !fails(function () { |
| nativeConstruct(function () { /* empty */ }); |
| }); |
| var FORCED = NEW_TARGET_BUG || ARGS_BUG; |
| |
| $({ target: 'Reflect', stat: true, forced: FORCED, sham: FORCED }, { |
| construct: function construct(Target, args /* , newTarget */) { |
| aFunction(Target); |
| anObject(args); |
| var newTarget = arguments.length < 3 ? Target : aFunction(arguments[2]); |
| if (ARGS_BUG && !NEW_TARGET_BUG) return nativeConstruct(Target, args, newTarget); |
| if (Target == newTarget) { |
| // w/o altered newTarget, optimization for 0-4 arguments |
| switch (args.length) { |
| case 0: return new Target(); |
| case 1: return new Target(args[0]); |
| case 2: return new Target(args[0], args[1]); |
| case 3: return new Target(args[0], args[1], args[2]); |
| case 4: return new Target(args[0], args[1], args[2], args[3]); |
| } |
| // w/o altered newTarget, lot of arguments case |
| var $args = [null]; |
| $args.push.apply($args, args); |
| return new (bind.apply(Target, $args))(); |
| } |
| // with altered newTarget, not support built-in constructors |
| var proto = newTarget.prototype; |
| var instance = create(isObject(proto) ? proto : Object.prototype); |
| var result = Function.apply.call(Target, instance, args); |
| return isObject(result) ? result : instance; |
| } |
| }); |