javascript全局变量封装模块实现代码_javascript技巧

/*global window,jQuery,validate_email,masterUI,$,rest*/
/** Enable ECMAScript "strict" operation for this function. See more:
* http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more/
* http://stackoverflow.com/questions/5020479/what-advantages-does-using-functionwindow-document-undefined-windo
* Q1: Why are window and document being fed instead of just being accessed normally?
* A1: Generally to fasten the identifier resolution process, having them as local variables can help (although IMO the performance improvements may be negligible).
* A2: Passing the global object is also a widely used technique on non-browser environments, where you don't have a window identifier at the global scope, e.g.:
* (function (global) {
* //..
* })(this); // this on the global execution context is the global object itself
* A3: Passing window and document allows the script to be more efficiently minified
*
* Q2: Why the heck is undefined being passed in?
* A1: This is made because the undefined global property in ECMAScript 3, is mutable, meaning that someone could change its value affecting your code, for example:
* undefined = true; // mutable
* (function (undefined) {
* alert(typeof undefined); // "undefined", the local identifier
* })(); // <-- no value passed, undefined by default
* If you look carefully undefined is actually not being passed (there's no argument on the function call),
* that's one of the reliable ways to get the undefined value, without using the property window.undefined.
*
*/
(function(window, document, undefined) {
"use strict";
window.test = {
init: function () {
"use strict";
alert("ok");
}
};
})(window, document);// no undefined parameter here to avoid using mutable window.undefined changed by other guy

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