var ERROR_MESSAGE = 'Function.prototype.bind called on incompatible '; var slice = Array.prototype.slice; var toStr = Object.prototype.toString; var funcType = '[object Function]'; module.exports = function bind(that) { var target = this; if (typeof target !== 'function' || toStr.call(target) !== funcType) { throw new TypeError(ERROR_MESSAGE + target); } var args = slice.call(arguments, 1); var bound; var binder = function () { if (this instanceof bound) { var result = target.apply( this, args.concat(slice.call(arguments)) ); if (Object(result) === result) { return result; } return this; } else { return target.apply( that, args.concat(slice.call(arguments)) ); } }; var boundLength = Math.max(0, target.length - args.length); var boundArgs = []; for (var i = 0; i < boundLength; i++) { boundArgs.push('$' + i); } bound = Function('binder', 'return function (' + boundArgs.join(',') + '){ 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; };