There are several good ways to define a function

4 ways to define a function

1. The most basic use as a separate function declaration.

The copy code is as follows:

 
function func(){} 
 or  
var func=function(){}; 

2. Use as a class constructor:

The copy code is as follows:

 
function class(){} 
class.prototype={}; 
var item=new class(); 

3. Used as a closure:

The copy code is as follows:

 
(function(){ 
//Independent scope
})(); 

4. Can be used as a selector:

The copy code is as follows:

 
var addEvent=new function(){ 
if(!-[1,]) return function(elem,type,func){attachEvent(elem,'on'+type,func);}; 
else return function(elem,type,func){addEventListener(elem,type,func,false);} 
};//Avoid duplicate judgments

5. Mixed application of the above four situations:

The copy code is as follows:

 
var class=new function(){ 
var privateArg;//Static private variable
function privateMethod=function(){};//Static private method
return function(){/* A true constructor *