为什么将IIFE分配给变量? [英] Why assign an IIFE to a variable?

问题描述

我一直在JavaScript和AngularJS中使用IIFE，并一直使用以下结构:

I've been using IIFE in JavaScript and in AngularJS and have been using the following structure:

方法1:

//IIFE Immediately Invoked Function Expression
(function () {


}());

但是，我经常看到以下情况，其中将变量分配给IIFE

However, I've seen the following often where a variable is assigned to the IIFE

方法2:

//IIFE Immediately Invoked Function Expression assigned to doStuff variable
var doStuff = (function () {


}());

注意:关于此模式是什么或IIFE是否的问题.这与为什么要在IIFE上使用返回变量 及其与Angular实践的关系有关.

NOTE: This question is NOT about what this pattern is or what an IIFE is. This is pertaining specifically to why one would use a return variable on an IIFE and its relation to Angular practices as well.

在Angular方法1中工作正常，但是在我看到的许多原始JS示例中，都使用了方法2.我的假设是doStuff中包含的任何内容都可以通过它进行调用.但是，我不确定这两种方法的确切推理或区别是100％不确定，需要一些帮助来了解何时使用不同的方法吗?

In Angular Method 1 works fine, but in many of the raw JS examples I see, Method 2 is used. My assumption is that anything encasulated in doStuff will be avliable via it and callable. However, I'm not 100% sure on the exact reasoning or distinction between the 2 methods and need some help understanding when to use the different methods?

推荐答案

方法2的原因是，您会在IIFE中找到返回的代码(通常，但不一定，对象或函数). IIFE返回的是最终被分配的东西.例如:

The reason for Method #2 is that you'll find code within the IIFE that returns something (typically, but not necessarily, an object or a function). What the IIFE returns is what ends up being assigned. E.g.:

//IIFE Immediately Invoked Function Expression assigned to doStuff variable
var doStuff = (function () {
    var privateInformationForDoStuff = 0;

    function doStuff() {
        console.log(++privateInformationForDoStuff);
    }

    return doStuff;
}());

在那里，变量最终是对函数的引用，该函数每次被调用时，都会给我们一个比上一次更高的数字. IIFE可以确保没有任何东西可以修改privateInformationForDoStuff变量，因为它完全是doStuff函数的私有变量.

There, the variable ends up being a reference to a function that, each time it's called, gives us a number higher than the previous time. The IIFE is there to ensure that nothing can modify the privateInformationForDoStuff variable, it's entirely private to the doStuff function.

此方法的常见用途是创建具有各种功能的对象，有时称为模块，这些对象可能还具有仅在模块"内共享的私人信息:

The common use of this is to create objects with various functions on them, sometimes called modules, which might also have private information that's only shared within the "module":

var MyApp = (function() {
    var privateModuleInformation;
    var morePrivateModuleInformation;
    // ...

    function doThis() {
        // ...
    }

    function doThat() {
        // ...
    }

    function doTheOther() {
        // ...
    }

    return {
        doThis: doThis,
        doThat: doThat,
        doTheOther: doTheOther
    };
})();

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