--- /dev/null
+'use strict';
+// https://tc39.github.io/proposal-setmap-offrom/
+var aFunction = require('../internals/a-function');
+var bind = require('../internals/function-bind-context');
+var iterate = require('../internals/iterate');
+
+module.exports = function from(source /* , mapFn, thisArg */) {
+ var length = arguments.length;
+ var mapFn = length > 1 ? arguments[1] : undefined;
+ var mapping, array, n, boundFunction;
+ aFunction(this);
+ mapping = mapFn !== undefined;
+ if (mapping) aFunction(mapFn);
+ if (source == undefined) return new this();
+ array = [];
+ if (mapping) {
+ n = 0;
+ boundFunction = bind(mapFn, length > 2 ? arguments[2] : undefined, 2);
+ iterate(source, function (nextItem) {
+ array.push(boundFunction(nextItem, n++));
+ });
+ } else {
+ iterate(source, array.push, { that: array });
+ }
+ return new this(array);
+};