将自动执行的匿名函数分配给javascript中的变量有什么好处? [英] What is the benefit of assigning a self executing anonymous function to a variable in javascript?

问题描述

我正在阅读帖子关于在窗口调整大小后如何触发函数的信息，并遇到了一些将自执行匿名函数分配给变量的示例:

I was reading a post about how to fire a function after a window resize was complete and came across some examples that assigned self executing anonymous functions to variables:

var delay = (function(){
    var timer = 0;
    return function(callback, ms){
        clearTimeout (timer);
        timer = setTimeout(callback, ms);
    };
})();

$(window).resize(function() {
    delay(function(){
      alert('Resize...');
      //...
    }, 500);
});

使函数操作数自动执行与传统用法相比有什么区别/好处?即

What is the difference/benefit of making the function operand self executing as opposed to it's traditional use? i.e.

var delay = function() { ... 

推荐答案

主要原因是命名空间变量.函数引入了新的变量范围.在上面的示例中，timer不会破坏全局名称空间，同时仍可用于需要它的代码.

The main reason for this is namespacing variables. Functions introduce a new variable scope. In the case of the above example, timer is not clobbering the global namespace while still being available to the code that needs it.

由于我显然需要澄清:

目标是在函数外部具有一个变量:

The goal is to have a variable outside the function:

var timer;

function delay() {
   // use timer
}

由于该变量位于函数内部，因此每次都会将其重新初始化.但是，我们希望在函数外提供一个持久值.

Because if the variable would be inside the function, it would be reinitialized every time. We want a persistent value outside the function though.

在上面的代码中，timer是一个全局变量.我们不想那个.为避免这种情况，我们将变量封闭在新的范围内，以便delay函数可以访问它，但不能全局访问:

In the above code timer is a global variable though. We don't want that. To avoid that, we close the variable up in a new scope so it's accessible to the delay function, but not globally:

var delay = (function () {
    var timer;

    return function () {
        // use timer
    };
})();

delay现在就像以前一样可以在其外部使用timer，但是timer不在全局范围内.

delay is now a function just as before which can use timer outside itself, yet timer is not in the global scope.

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