85 lines
2.0 KiB
JavaScript
85 lines
2.0 KiB
JavaScript
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'use strict';
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/* eslint no-invalid-this: 1 */
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var ERROR_MESSAGE = 'Function.prototype.bind called on incompatible ';
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var toStr = Object.prototype.toString;
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var max = Math.max;
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var funcType = '[object Function]';
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var concatty = function concatty(a, b) {
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var arr = [];
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for (var i = 0; i < a.length; i += 1) {
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arr[i] = a[i];
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}
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for (var j = 0; j < b.length; j += 1) {
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arr[j + a.length] = b[j];
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}
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return arr;
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};
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var slicy = function slicy(arrLike, offset) {
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var arr = [];
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for (var i = offset || 0, j = 0; i < arrLike.length; i += 1, j += 1) {
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arr[j] = arrLike[i];
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}
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return arr;
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};
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var joiny = function (arr, joiner) {
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var str = '';
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for (var i = 0; i < arr.length; i += 1) {
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str += arr[i];
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if (i + 1 < arr.length) {
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str += joiner;
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}
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}
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return str;
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};
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module.exports = function bind(that) {
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var target = this;
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if (typeof target !== 'function' || toStr.apply(target) !== funcType) {
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throw new TypeError(ERROR_MESSAGE + target);
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}
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var args = slicy(arguments, 1);
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var bound;
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var binder = function () {
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if (this instanceof bound) {
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var result = target.apply(
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this,
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concatty(args, arguments)
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);
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if (Object(result) === result) {
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return result;
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}
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return this;
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}
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return target.apply(
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that,
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concatty(args, arguments)
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);
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};
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var boundLength = max(0, target.length - args.length);
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var boundArgs = [];
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for (var i = 0; i < boundLength; i++) {
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boundArgs[i] = '$' + i;
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}
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bound = Function('binder', 'return function (' + joiny(boundArgs, ',') + '){ return binder.apply(this,arguments); }')(binder);
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if (target.prototype) {
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var Empty = function Empty() {};
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Empty.prototype = target.prototype;
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bound.prototype = new Empty();
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Empty.prototype = null;
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}
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return bound;
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};
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