1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
|
// 26.1.2 Reflect.construct(target, argumentsList [, newTarget])
var $export = require('./_export')
, create = require('./_object-create')
, aFunction = require('./_a-function')
, anObject = require('./_an-object')
, isObject = require('./_is-object')
, fails = require('./_fails')
, bind = require('./_bind')
, rConstruct = (require('./_global').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(){}
return !(rConstruct(function(){}, [], F) instanceof F);
});
var ARGS_BUG = !fails(function(){
rConstruct(function(){});
});
$export($export.S + $export.F * (NEW_TARGET_BUG || ARGS_BUG), 'Reflect', {
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 rConstruct(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
, instance = create(isObject(proto) ? proto : Object.prototype)
, result = Function.apply.call(Target, instance, args);
return isObject(result) ? result : instance;
}
});
|
