在 jQuery 核心源代码中传入未定义的参数
我注意到在 jQuery 核心中，传入的两个参数之一是未定义的。
(function( window, undefined ) {
// Use the correct document accordingly with window argument (sandbox)
var document = window.document;
var jQuery = (function() {
// ...defintion of the rest of the core...
window.jQuery = window.$ = jQuery;
})(window);
谁能解释为什么第二个参数是未定义？
提前致谢！
I noticed that in the jQuery core, one of the two arguments passed in is undefined.
(function( window, undefined ) {
// Use the correct document accordingly with window argument (sandbox)
var document = window.document;
var jQuery = (function() {
// ...defintion of the rest of the core...
window.jQuery = window.$ = jQuery;
})(window);
Can anyone explain why the second argument is undefined?
Thanks in advance!
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Undefined 是一种类型，但也是一个全局变量。
您可以通过执行
undefine =whatever来让模块覆盖 undefined 的值。jQuery 使用立即函数来确定窗口和未定义的范围。
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/undefined
Undefined is a type but is also a global variable.
You can have a module that overwrites the value of undefined by doing
undefined = whatever.jQuery uses a immediate function to scope window and undefined.
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/undefined
由于有人可以像这样覆盖 undefined ，因此
您的立即函数的代码将按应有的方式传递它（保持未定义）。我认为它在 我从 jQuery 中学到的 10 件事中提到过来源。
Since someone could overwrite undefined like this
Code of your immediate function will pass it as it should be (stay undefined). I think it's mentioned in 10 Things I Learned from the jQuery Source.