javascript IIFE 立即调用
参考链接:http://nuysoft.com/2013/04/15/angry-birds-of-javascript-red-bird-iife/
#####代码示例
var bird = (function(){
var type = "red"，
power = "IIFE"，
attack = function(){
console.log(type + " XXX " + power + "!");
}；
return {
type: type,
attack: attack
}
}());
console.log(bird.type); //输出red
console.log(bird.power);//undefined
console.log(bird.attack()); //输出red XXX IIFE!
######Refactor (function(bird){ var power = “IIFE”; bird.type = “mlx”; bird.attack = function(){ console.log(bird.type + “ XXX “ + power + “!”); }; }(window.bird = window.bird || {}));
console.log(bird.type);
console.log(bird.power);
console.log(bird.attack());
####变量作用域 在 JavaScript 中，变量的作用域由函数作用域决定，而不是块级作用域。（所谓块级作用域就是大括号包裹的部分，这个特性和java 等语言是有区别的）
#####代码示例
var fn = function(){
if(3>2){
var a = 3;
}
else{
}
alert(a);
}
fn(); //输出 3 ⟺
