JavaScript用全局变量封装模块

下面的代码是我的测试代码，注释很重要：

[plain]
/* 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?                                        &

补充：web前端 , JavaScript ,

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