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- 'use strict';
- var uncurryThis = require('../internals/function-uncurry-this');
- var aCallable = require('../internals/a-callable');
- var isObject = require('../internals/is-object');
- var hasOwn = require('../internals/has-own-property');
- var arraySlice = require('../internals/array-slice');
- var NATIVE_BIND = require('../internals/function-bind-native');
- var $Function = Function;
- var concat = uncurryThis([].concat);
- var join = uncurryThis([].join);
- var factories = {};
- var construct = function (C, argsLength, args) {
- if (!hasOwn(factories, argsLength)) {
- for (var list = [], i = 0; i < argsLength; i++) list[i] = 'a[' + i + ']';
- factories[argsLength] = $Function('C,a', 'return new C(' + join(list, ',') + ')');
- } return factories[argsLength](C, args);
- };
- // `Function.prototype.bind` method implementation
- // https://tc39.es/ecma262/#sec-function.prototype.bind
- module.exports = NATIVE_BIND ? $Function.bind : function bind(that /* , ...args */) {
- var F = aCallable(this);
- var Prototype = F.prototype;
- var partArgs = arraySlice(arguments, 1);
- var boundFunction = function bound(/* args... */) {
- var args = concat(partArgs, arraySlice(arguments));
- return this instanceof boundFunction ? construct(F, args.length, args) : F.apply(that, args);
- };
- if (isObject(Prototype)) boundFunction.prototype = Prototype;
- return boundFunction;
- };
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