2 var ctx = require('./_ctx')
3 , $export = require('./_export')
4 , toObject = require('./_to-object')
5 , call = require('./_iter-call')
6 , isArrayIter = require('./_is-array-iter')
7 , toLength = require('./_to-length')
8 , createProperty = require('./_create-property')
9 , getIterFn = require('./core.get-iterator-method');
11 $export($export.S + $export.F * !require('./_iter-detect')(function(iter){ Array.from(iter); }), 'Array', {
12 // 22.1.2.1 Array.from(arrayLike, mapfn = undefined, thisArg = undefined)
13 from: function from(arrayLike/*, mapfn = undefined, thisArg = undefined*/){
14 var O = toObject(arrayLike)
15 , C = typeof this == 'function' ? this : Array
16 , aLen = arguments.length
17 , mapfn = aLen > 1 ? arguments[1] : undefined
18 , mapping = mapfn !== undefined
20 , iterFn = getIterFn(O)
21 , length, result, step, iterator;
22 if(mapping)mapfn = ctx(mapfn, aLen > 2 ? arguments[2] : undefined, 2);
23 // if object isn't iterable or it's array with default iterator - use simple case
24 if(iterFn != undefined && !(C == Array && isArrayIter(iterFn))){
25 for(iterator = iterFn.call(O), result = new C; !(step = iterator.next()).done; index++){
26 createProperty(result, index, mapping ? call(iterator, mapfn, [step.value, index], true) : step.value);
29 length = toLength(O.length);
30 for(result = new C(length); length > index; index++){
31 createProperty(result, index, mapping ? mapfn(O[index], index) : O[index]);
34 result.length = index;