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