闭包也就这玩意

闭包也叫closure这东西听起来挺玄乎，《js犀牛书》上搞了一计数器作为例子，如下：

 

function counter() {
    var n = 0;
    return {
        count: function() { return n++; },
        reset: function() { n = 0; }
    };
}
var c = counter(), d = counter();   // Create two counters
c.count()                           // => 0
d.count()                           // => 0: they count independently
c.reset()                           // reset() and count() methods share state
c.count()                           // => 0: because we reset c
d.count()                           // => 1: d was not reset

 我看了半天，没觉得有啥大不了的，感觉很自然，我转念一想，这不就是把函数当成面向对象中的类了嘛

 

public class counter() {
    private int n = 0;
  
    public int count{ return n++; },
    public void reset{ n = 0; }
}
counter c = new counter();
counter d = new counter();   // Create two counters
c.count()                           // => 0
d.count()                           // => 0: they count independently
c.reset()                           // reset() and count() methods share state
c.count()                           // => 0: because we reset c
d.count()                           // => 1: d was not reset

 肿么样？是这回事吧，其实闭包就是：

“把父函数当作对象（object）使用，把闭包当作它的公用方法（Public Method），把内部变量当作它的私有属性（private value）。”

欢迎拍砖。

 

一个较为详细的关于闭包的文章如下：

深入理解js闭包