# MDN **判断是不是函数** ``` Object.prototype.toString.call(callback) != "[object Function]" ``` **创建指定长度的空数组** ``` new Array(10) //(10)[empty × 10] ``` 闭包速览 -- ```javascript var f1 = function(args){ //do something return f1 } f1(args) ``` ```javascript var f1 = function(){ var a = ...