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35 lines
1.4 KiB
35 lines
1.4 KiB
3 years ago
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'use strict';
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var global = require('../internals/global');
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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 = global.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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