Yang Guo | 4fd355c | 2019-09-19 10:59:03 +0200 | [diff] [blame^] | 1 | 'use strict'; |
| 2 | |
| 3 | /* eslint no-invalid-this: 1 */ |
| 4 | |
| 5 | var ERROR_MESSAGE = 'Function.prototype.bind called on incompatible '; |
| 6 | var slice = Array.prototype.slice; |
| 7 | var toStr = Object.prototype.toString; |
| 8 | var funcType = '[object Function]'; |
| 9 | |
| 10 | module.exports = function bind(that) { |
| 11 | var target = this; |
| 12 | if (typeof target !== 'function' || toStr.call(target) !== funcType) { |
| 13 | throw new TypeError(ERROR_MESSAGE + target); |
| 14 | } |
| 15 | var args = slice.call(arguments, 1); |
| 16 | |
| 17 | var bound; |
| 18 | var binder = function () { |
| 19 | if (this instanceof bound) { |
| 20 | var result = target.apply( |
| 21 | this, |
| 22 | args.concat(slice.call(arguments)) |
| 23 | ); |
| 24 | if (Object(result) === result) { |
| 25 | return result; |
| 26 | } |
| 27 | return this; |
| 28 | } else { |
| 29 | return target.apply( |
| 30 | that, |
| 31 | args.concat(slice.call(arguments)) |
| 32 | ); |
| 33 | } |
| 34 | }; |
| 35 | |
| 36 | var boundLength = Math.max(0, target.length - args.length); |
| 37 | var boundArgs = []; |
| 38 | for (var i = 0; i < boundLength; i++) { |
| 39 | boundArgs.push('$' + i); |
| 40 | } |
| 41 | |
| 42 | bound = Function('binder', 'return function (' + boundArgs.join(',') + '){ return binder.apply(this,arguments); }')(binder); |
| 43 | |
| 44 | if (target.prototype) { |
| 45 | var Empty = function Empty() {}; |
| 46 | Empty.prototype = target.prototype; |
| 47 | bound.prototype = new Empty(); |
| 48 | Empty.prototype = null; |
| 49 | } |
| 50 | |
| 51 | return bound; |
| 52 | }; |