学习JavaScript（2）
学习JavaScript（二）Checking if a Variable Exists(function(name){alert(Hello + name + !)})(dud
学习JavaScript（二）
Checking if a Variable Exists
(function(name){alert('Hello ' + name + '!');})('dude')One good reason for using self-invoking anonymous functions is to have some
work done without creating global variables.
A drawback, of course, is that you cannot execute the same function twice
