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