请解释这个requestAnimationFrame成语

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问题描述

有很多地方（例如）修复 window.requestAnimationFrame 如下。我不明白为什么分配的右侧包含在函数调用中。

there are a lot of places (e.g. How to use requestAnimationFrame?) that fix window.requestAnimationFrame as below. I do not understand why the right hand side of the assignment is wrapped in to a function call.


window.requestAnimFrame = (function(){
    return window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    function(callback){
        window.setTimeout(callback, 1000 / 60);
    };
})();

推荐答案

我想知道同样的事情之前。我很确定谷歌真的很喜欢闭包。当然，那里没有一个变量，这是一个安全的事情。

I've wondered the same thing before. I'm pretty sure Google just really likes closures. Granted there is not one variable in there, it's a 'safe' thing to do.

据我所知，这是完全相同的事情，没有任何改变干扰名称空间（使用类似闭包的一般原因）：

As far as I can tell, this is the exact same thing, without any change of interfering with namespaces (a general reason to use a closure like that):

window.requestAnimFrame = 
    window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    function(callback){
        window.setTimeout(callback, 1000 / 60);
    };

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