2 // https://tc39.github.io/proposal-setmap-offrom/
3 var bind = require('../internals/function-bind-context');
4 var call = require('../internals/function-call');
5 var aCallable = require('../internals/a-callable');
6 var aConstructor = require('../internals/a-constructor');
7 var iterate = require('../internals/iterate');
11 module.exports = function from(source /* , mapFn, thisArg */) {
12 var length = arguments.length;
13 var mapFn = length > 1 ? arguments[1] : undefined;
14 var mapping, array, n, boundFunction;
16 mapping = mapFn !== undefined;
17 if (mapping) aCallable(mapFn);
18 if (source == undefined) return new this();
22 boundFunction = bind(mapFn, length > 2 ? arguments[2] : undefined);
23 iterate(source, function (nextItem) {
24 call(push, array, boundFunction(nextItem, n++));
27 iterate(source, push, { that: array });
29 return new this(array);