2 var bind = require('../internals/function-bind-context');
3 var toObject = require('../internals/to-object');
4 var callWithSafeIterationClosing = require('../internals/call-with-safe-iteration-closing');
5 var isArrayIteratorMethod = require('../internals/is-array-iterator-method');
6 var toLength = require('../internals/to-length');
7 var createProperty = require('../internals/create-property');
8 var getIteratorMethod = require('../internals/get-iterator-method');
10 // `Array.from` method implementation
11 // https://tc39.es/ecma262/#sec-array.from
12 module.exports = function from(arrayLike /* , mapfn = undefined, thisArg = undefined */) {
13 var O = toObject(arrayLike);
14 var C = typeof this == 'function' ? this : Array;
15 var argumentsLength = arguments.length;
16 var mapfn = argumentsLength > 1 ? arguments[1] : undefined;
17 var mapping = mapfn !== undefined;
18 var iteratorMethod = getIteratorMethod(O);
20 var length, result, step, iterator, next, value;
21 if (mapping) mapfn = bind(mapfn, argumentsLength > 2 ? arguments[2] : undefined, 2);
22 // if the target is not iterable or it's an array with the default iterator - use a simple case
23 if (iteratorMethod != undefined && !(C == Array && isArrayIteratorMethod(iteratorMethod))) {
24 iterator = iteratorMethod.call(O);
27 for (;!(step = next.call(iterator)).done; index++) {
28 value = mapping ? callWithSafeIterationClosing(iterator, mapfn, [step.value, index], true) : step.value;
29 createProperty(result, index, value);
32 length = toLength(O.length);
33 result = new C(length);
34 for (;length > index; index++) {
35 value = mapping ? mapfn(O[index], index) : O[index];
36 createProperty(result, index, value);
39 result.length = index;