在javascript中提升 [英] Hoisting in javascript

问题描述

之前我问了一个问题，有人给我一个指南，我看了它，我看到了这个

I asked a question before and somebody give me a guide and I read it and I saw this

  var temp = setTimeout,
  setTimeout = function() {};

他说由于JavaScript挂起，temp将不确定，我不明白为什么
不应该那样吗？

He said that temp will be undefined due to JavaScript hoisting and I dont understand why Its not should be like that?

    var temp;
    temp = setTimeout;
    setTimeout = function() {};

为什么它未定义？

推荐答案

这是不一样的。您的多个 var 声明还声明 setTimeout ：

This is not the same. Your multiple var declaration also declares setTimeout:

var temp = setTimeout,
    setTimeout = function() {};

被提升至

var temp; // = undefined
var setTimeout; // = undefined
temp = setTimeout;
setTimeout = function() {};

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