自调用函数jQuery [英] Self-invoking function jQuery

问题描述

我注意到在某些地方，jQuery代码包装在如下所示的自调用函数中.为什么要这样做，在什么情况下有用，在什么情况下是不必要的样板?

I noticed that in some places, jQuery code is wrapped in a self-invoking function like below. Why is this done, in what cases is this useful and in what cases is an unnecessary boilerplate?

function( $ ) {
  ...
}( jQuery );

推荐答案

简短答案:防止变量名冲突.并非总是需要它，但是为了创建无冲突的可重用代码，这是一种很好的做法.

The short answer: To prevent variable name conflicts. It is not always needed, but good practice in order to create conflict free reusable code.

长答案:在javascript中，$符号只是另一个变量. jQuery之所以使用它，是因为它是一个很好的速记方式，而不必每次都键入jQuery，但是其他任何代码(包括其他库)也可以.

The long answer: In javascript the $ symbol is just another variable. jQuery uses it because it is a nice shorthand instead of having to type out jQuery each time, but so can any other code (including other libraries).

为防止与同一范围内的变量的其他用途(在本例中为$，在全局"范围内)发生冲突，通常将代码包装在带有无冲突"变量的自调用函数中作为函数参数传递.然后，这将创建一个新的作用域，其中您的变量将不会干扰该变量的其他使用.这样，您就可以传递完整的命名变量&可以在匿名函数中以您想要的任何名称使用它.

To prevent conflict with other uses of a variable at the same scope (in this case $ at the "global" scope) it is common for code to be wrapped in a self-invoking function with the "conflict-free" variables passed as the function parameters. This then creates a new scope where your variable won't interfere with other uses of that variable. That way you can pass the full named variable & uses it with whatever name you want within the anonymous function.

因此，在创建无冲突的可重用代码时，使用此方法是一个好习惯:

So, when creating conflict free reusable code it is good practice to use this methodology:

(function( $ ) {
  ...
})( jQuery );

沿着这些行，您还将看到以下格式:

Along these lines you will also see the following format:

(function( $, window, undefined ) {
  ...
})( jQuery, window );

在这种情况下，undefined只是为了提高可读性，以指示没有更多的参数传递给该函数.

In this instance undefined is simply used for readability to indicating that no more arguments are passed to the function.

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