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.es/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; } });