demo1

 var demo = (function(){
        var that ={}
        that.register = function(ns,maker){
            var step = that;
            var NSlist = ns.split('.')
            while(k = NSlist.shift()){
                if(NSlist.length){
                    if(step[k]===undefined){
                        step[k] = {}
                    }
                    step = step[k]
                }else{
                    if(step[k]===undefined){
                        try {
                            step[k] = maker()
                        } catch(exp) {}
                    }
                }
            }
        }
        return that
    }())
    demo.register('core.arr.inArray',function(){
        return function(o){
            return Object.prototype.toString.call(o)==='[object Array]'
        }
    })
    var arr = [11,33,55]
    console.log( demo.core.arr.inArray(arr))

demo2

 ;(function(){
        var demo2 = function(){}
        demo2.prototype={
                isArray : function(o){
                    return Object.prototype.toString.call(o)==='[object Array]'
                }
        }
        window.demo2 = demo2
    }())
    var arr2 =[22,66];
    var user1 = new demo2();
   console.log( user1.isArray(arr2))

demo3

 var demo3 = {
        isArray : function(o){
            return Object.prototype.toString.call(o)==='[object Array]'
        }
    }
    console.log(demo3.isArray(arr))

demo4

 var demo4 = (function(){
        return {
            isArray : function(o){
                return Object.prototype.toString.call(o)==='[object Array]'
            }
        }
    }())
    console.log( demo4.isArray(arr))

不知道这两种写法 哪种更优一点 哪种适用于什么情况
还请知道的 指导一下