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- 'use strict';
- var ERROR_MESSAGE = 'Function.prototype.bind called on incompatible ';
- var toStr = Object.prototype.toString;
- var max = Math.max;
- var funcType = '[object Function]';
- var concatty = function concatty(a, b) {
- var arr = [];
- for (var i = 0; i < a.length; i += 1) {
- arr[i] = a[i];
- }
- for (var j = 0; j < b.length; j += 1) {
- arr[j + a.length] = b[j];
- }
- return arr;
- };
- var slicy = function slicy(arrLike, offset) {
- var arr = [];
- for (var i = offset || 0, j = 0; i < arrLike.length; i += 1, j += 1) {
- arr[j] = arrLike[i];
- }
- return arr;
- };
- var joiny = function (arr, joiner) {
- var str = '';
- for (var i = 0; i < arr.length; i += 1) {
- str += arr[i];
- if (i + 1 < arr.length) {
- str += joiner;
- }
- }
- return str;
- };
- module.exports = function bind(that) {
- var target = this;
- if (typeof target !== 'function' || toStr.apply(target) !== funcType) {
- throw new TypeError(ERROR_MESSAGE + target);
- }
- var args = slicy(arguments, 1);
- var bound;
- var binder = function () {
- if (this instanceof bound) {
- var result = target.apply(
- this,
- concatty(args, arguments)
- );
- if (Object(result) === result) {
- return result;
- }
- return this;
- }
- return target.apply(
- that,
- concatty(args, arguments)
- );
- };
- var boundLength = max(0, target.length - args.length);
- var boundArgs = [];
- for (var i = 0; i < boundLength; i++) {
- boundArgs[i] = '$' + i;
- }
- bound = Function('binder', 'return function (' + joiny(boundArgs, ',') + '){ return binder.apply(this,arguments); }')(binder);
- if (target.prototype) {
- var Empty = function Empty() {};
- Empty.prototype = target.prototype;
- bound.prototype = new Empty();
- Empty.prototype = null;
- }
- return bound;
- };
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