将自执行匿名函数分配给 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如何在完成窗口大小调整后触发函数，并遇到了一些将自执行匿名函数分配给变量的示例:

var delay = (function(){无功计时器= 0;返回函数(回调，毫秒){clearTimeout(定时器)；定时器 = 设置超时(回调，毫秒)；};})();$(window).resize(function() {延迟(功能(){alert('调整大小...');//...}, 500);});

与传统用途相比，使函数操作数自执行有什么区别/好处?即

var delay = function() { ...

解决方案

造成这种情况的主要原因是命名空间变量.函数引入了一个新的变量作用域.在上面的例子中，timer 不会破坏全局命名空间，同时仍然可供需要它的代码使用.

<小时>

因为我显然需要澄清:

目标是在函数外有一个变量:

var 定时器；函数延迟(){//使用定时器}

因为如果变量在函数内部，它每次都会被重新初始化.不过，我们希望在函数之外有一个持久值.

在上面的代码中 timer 是一个全局变量.我们不想要那样.为了避免这种情况，我们将变量关闭在一个新的作用域中，以便 delay 函数可以访问它，但不能全局访问:

var delay = (function() {无功定时器；返回函数(){//使用定时器};})();

delay 现在是一个和以前一样的函数，它可以在自身之外使用 timer，但 timer 不在全局范围内.>

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);
});

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

var delay = function() { ... 

解决方案

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.

---

Since I apparently need to clarify:

The goal is to have a variable outside the function:

var timer;

function delay() {
   // use timer
}

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

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 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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