1'use strict'; 2 3/* eslint no-invalid-this: 1 */ 4 5var ERROR_MESSAGE = 'Function.prototype.bind called on incompatible '; 6var slice = Array.prototype.slice; 7var toStr = Object.prototype.toString; 8var funcType = '[object Function]'; 9 10module.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}; 53