在jQuery中匿名函数包装器的目的是什么？ [英] What is the purpose of the anonymous function wrapper in jQuery?

问题描述

jQuery开始在匿名函数中包装所有代码：

jQuery starts off wrapping all of it's code in an anonymous function:

(function ( window, undefined) {
   /*
   ...jquery code...
   */
}) (window);

我知道在读取整个脚本后立即执行该函数，但是目的是什么争论？一个是全局对象引用，另一个是属性引用。

I get that the function is executed immediately upon the entire script being read, but what is the purpose of the arguments? One is a global object reference, the other is a property reference.

现在，我记得在脚本开发的早期，undefined实际上被定义为其他东西（我是还记得那个吗？）那是否与此相关？

Now, I remember that earlier in the script development, undefined actually got defined as something else (am I remembering that right?). Was that related to this?

此外，看起来该函数被用作运算符？就像它在上面一样，我根本不理解语句的语法。也许有上下文会有所帮助？

Also, it looks like the function is being used as an operator? Just like it is above, I don't understand the syntax of the statement at all. Maybe there is context that would help?

推荐答案

包装器做了很多事情：

function(window,undefined)

为函数提供窗口和 undefined 变量

匿名调用}）（窗口）; 将窗口变量传递给脚本。

the anonymous call })(window); passes the window variable to the script.

如果用户覆盖了window对象，他们可以很容易地修改脚本以使用正确的窗口变量，即：

If a user overrides the window object, they will easily be able to modify the script to use the correct window variable i.e.:

(function(window,undefined){})(w);

缺少第二个参数设置 undefined 变量的值为 undefined ，这可以防止程序员通过覆盖 undefined 来搞乱jQuery。

The lack of a second parameter being passed sets the undefined variable to have a value of undefined which prevents a programmer from messing up jQuery by overriding undefined.

这篇关于在jQuery中匿名函数包装器的目的是什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！