带闭环的环路保存状态 [英] For-loop saving state with closure

问题描述

原谅我，如果这可能是一个noobie问题，但这应该工作不应该吗？

Forgive me if this might be a bit of a noobie question, but this should work shouldn't it?

var elems = [1,2,3,4,5]

for (var i = 0; i <elems.length; i++) {
    return (function(e){
        console.log(e)
    })(i);
}

意味着应该吐出

>>node file.js
1
2
3
4
5

由于某种原因，这不是这样做的。而是当它在终端运行时，它会输出

For some reason this isn't doing this. Rather when it is run in terminal, it spits out

>>node file.js
1

我缺少什么？

推荐答案

因为您在此语句中立即返回由IIFE返回的值

Because you are returning the value returned by the IIFE immediately, in this statement

return (function(e){
    console.log(e)
})(i);

因为IIFE只是输出 0 不显式返回任何值，JavaScript将默认返回 undefined ，立即退出。要解决这个问题，只需删除 return 关键字

since the IIFE just prints 0 and doesn't return anything explicitly, JavaScript will return undefined by default and exit immediately. To fix this, just drop the return keyword,

(function(e){
    console.log(e)
})(i);

---

PS：你曾经想过，为什么上述代码中的 return 语句有效？想想它，它不是在一个函数内。然后在技术上它的一个错误，对吧？ ;-)我在这个问题中详细解释了这一点。

---

PS: Have you ever wondered, why the return statement in the above code works? To think about it, it is not inside a function. Then technically its an error, right? ;-) I explained this in detail, in this question.

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