Javascript包装匿名函数内的代码 [英] Javascript wrapping code inside anonymous function

问题描述

我需要帮助理解jQuery插件创作的这种模式。有人可以为我解释一下这段简单的代码吗？

I need help understanding this pattern for jQuery plugin authoring. Can somebody explain this simple bit of code for me?

(function($) { /* Code here */ })(jQuery);

我知道这是为了避免与使用相同 $ <的不同插件发生冲突/ code>字符，但不知何故无法理解它是如何工作的。参数 $ 与已解析的 jQuery 对象有什么关系？

I know this is to avoid conflict with different plugins using the same $ character but somehow cannot get around my head to understand how it works. What relation does the parameter $ has to the jQuery object that got parsed in?

推荐答案

让我们打破这个：

(function($) { /* Code here */ })(jQuery);

首先，构造：

(function() {})();

创建一个立即执行的函数表达式（通常称为IIFE）。这是一个立即执行而不是现在定义的函数，但稍后调用。它本质上是一个匿名（未命名）函数，它被定义然后立即执行。

creates an immediately executed function expression (often called IIFE). This is a function that is executed immediately rather than defined now, but called later. It is essentially an anonymous (unnamed) function that is defined and then executed right away.

然后，将jQuery传递给它：

Then, passing jQuery to it like this:

(function() {})(jQuery);

将jQuery作为该立即执行函数的第一个参数传递。然后，将第一个参数命名为 $ ，将函数内部的符号定义为与传递的第一个参数对应。

passes jQuery as the first argument to that immediately executed function. Then, naming that first argument as $ defines that symbol inside the function to correspond to the first argument that is passed.

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

以展开形式显示如下：

(function($) {
    // you can use $ here to refer to jQuery
})(jQuery);

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jQuery插件有一些好处作者：

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There a couple nice thing about this for jQuery plugin authors:

1. IIFE创建一个本地函数上下文，因此您可以为插件提供全局变量，但实际上并不是全局变量，因此不会污染或与实际的全局变量命名空间冲突。

1. The IIFE creates a local function context so you can have variables which are "global" for your plug-in, but are not actually global variables and thus don't pollute or conflict with the actual global variable namespace.

您可以使用 $进行编程对于jQuery，无论主机程序是否实际具有为jQuery定义的，因为您已在函数中本地定义了 $ 。

You can program with $ for jQuery, whether or not the host program actually has that defined for jQuery because you've defined $ locally within your function.

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