Use of JavaScript closures

Today, I learned the following JavaScript language, never thought about why to use anonymous and closures, for JS local variables and the concept of global understanding is not deep, consider the following code:

JS code function f1 () {var n=999;　　　　Nadd=function () {n+=1} function F2 () {alert (n);　　} return F2;　　} var result=f1 (); Result ();　　999 Nadd (); Result (); 1000

If the variable n is defined as a global variable, it will always be stored in memory, unless the browser is closed, but in some cases we have to use some variables frequently, then the closure method can be used to meet the needs, but it should be noted that:

Because the closure will make the variables in the function are stored in memory, memory consumption is very large, so can not abuse closures, otherwise it will cause the performance of the Web page, in IE may lead to memory leaks. The workaround is to remove all unused local variables before exiting the function. Here is a quote from an article on the Web: http://www.jb51.net/article/24101.htm

Use of JavaScript closures