javascript 命名空间,学习

一、

(function(){
                var _NS=function(){

                }
                _NS.prototype.alert=function(){
                    console.log('test');
                }
                window.NS=new _NS();
            })();

二、

// 声明一个全局对象Namespace，用来注册命名空间
Namespace = new Object();

// 全局对象仅仅存在register函数，参数为名称空间全路径，如"Grandsoft.GEA"
Namespace.register = function(fullNS)
{
    // 将命名空间切成N部分, 比如Grandsoft、GEA等
    var nsArray = fullNS.split('.');
    var sEval = "";
    var sNS = "";
    for (var i = 0; i < nsArray.length; i++)
    {
        if (i != 0) sNS += ".";
         sNS += nsArray[i];
        // 依次创建构造命名空间对象（假如不存在的话）的语句
        // 比如先创建Grandsoft，然后创建Grandsoft.GEA，依次下去
         sEval += "if (typeof(" + sNS + ") == 'undefined') " + sNS + " = new Object();"
     }
    if (sEval != "") eval(sEval);
}

// 注册命名空间Grandsoft.GEA, Grandsoft.GCM
Namespace.register("Grandsoft.GEA");
Namespace.register("Grandsoft.GCM");

// 在Grandsoft.GEA命名空间里面声明类Person
Grandsoft.GEA.Person = function(name, age)
{
    this.name = name;
    this.age = age;
}

// 给类Person添加一个公共方法show()
Grandsoft.GEA.Person.prototype.show = function()
{
     alert(this.name + " is " + this.age + " years old!");
}

// 演示如何使用类Person
var p = new Grandsoft.GEA.Person("yanglf", 25);
p.show();

三、

var YAHOO = window.YAHOO || {};

YAHOO.namespace = function(ns) {

    if (!ns || !ns.length) {
        return null;
     }

    var levels = ns.split(".");
    var nsobj = YAHOO;

    // YAHOO is implied, so it is ignored if it is included
    for (var i=(levels[0] == "YAHOO") ? 1 : 0; i<levels.length; ++i) {
         nsobj[levels[i]] = nsobj[levels[i]] || {};
         nsobj = nsobj[levels[i]];
     }

    return nsobj;
};

YAHOO.extend = function(subclass, superclass) {
    var f = function() {};
     f.prototype = superclass.prototype;
     subclass.prototype = new f();
     subclass.prototype.constructor = subclass;
     subclass.superclass = superclass.prototype;
    if (superclass.prototype.constructor == Object.prototype.constructor) {
         superclass.prototype.constructor = superclass;
     }
};

YAHOO.namespace("util");
YAHOO.namespace("widget");
YAHOO.namespace("example");

四、

function namespace(ns){
        if(typeof(ns)!="string")return;
        ns=ns.split(".");
        var o,ni;
        for(var i=0,len=ns.length;i<len,ni=ns[i];i++){
            try{o=(o?(o[ni]=o[ni]||{}):(eval(ni+"="+ni+"||{}")))}catch(e){o=eval(ni+"={}")}
        }
    }
/*
    function a(){return 5}
    namespace("a.b");
    alert(a);
    alert(a.b)
    namespace("test.test.abc")
    test.test.abc.func1=function(){
        alert('func1 run')
    }
    alert(test.test)
    test.test.abc.func1();
*/