JS- 封装、继承、多态

转载: http://www.cnblogs.com/silence516/articles/1509456.html


JS- 封装、继承、多态

Javascript是一门解释型的语言，是基于对象的，并不是真正的面向对象的语言，对变量类型的应用也是宽松的，其实它同样可以模拟面向对象的功能：

var newfun1 = new myfun1();
newfun1.public1(); //这是私有属性
alert(newfun1.publicvar);//这是实例属性
alert(newfun1.private1); // undefined   newfun1.privateMethod(); //运行错误
 

function myfun2(){
}
myfun2.staticvar = "这是静态属性";
myfun2.staticmethod = function(){
    alert(myfun2.staticvar);
}
var newfun2 = new myfun2();
//newfun2.staticmethod();//运行错误;
alert(newfun2.staticvar);//undefined

//静态私有成员
var myfun3 = (function(){
    function privateProperty(){
    
    }
    privateProperty.staticvar = "这是静态私有成员";
    privateProperty.staticmethod = function(){
        alert(privateProperty.staticvar);
    }
     privateProperty.staticmethod();
     return privateProperty
})();

//静态类
var funcount = 0;
var myfun4 = new function(){
    funcount++;
    this.printCount = function(){
        alert(funcount);
    }
}
myfun4.printCount(); //输出1;
myfun4.printCount(); //输出1;
myfun4.prototype.amethod = function(){
    alert("原型对象");
}//运行错误
var newfun4 = new myfun4();
newfun4.amethod();

//运行错误,说明myfun3创建并实例化之后就不能再为它添加方法,属性
new myfun3.constructor().printCount();//如果你确实想实例化,这样也可以.
//原型继承
var myfun5 = function(){

}
myfun5.prototype.myfun5_extend = function(){
    alert("这是原型继承的");
}
var myfun5_sub = function(){

}
myfun5_sub.prototype = new myfun5();
var newfun5 = new myfun5_sub();
newfun5.myfun5_extend(); //这是原型继承的
//调用继承
var myfun6 = function(){
    this.method_p = function(){
        alert("这是调用继承的");
    }
}
var myfun6_sub = function(){
    myfun6.call(this);
}

var newfun6 = new myfun6_sub();
newfun6.method_p();//这是调用继承的
//覆盖
var myfun7 = function(){
    this.method = function(){
        alert("这是父对象方法");
    }
}
var myfun7_sub = function(){
    this.method = function(){
        alert("这是子对象方法");
    }
}
myfun7_sub.prototype = new myfun7();
var newfun7 = new myfun7_sub();
newfun7.method(); //这是子对象方法,父对象方法被覆盖了.
//多态
function myfun8(a, b){
    var a = a;
    var b = b;
    if (typeof a == "number" && typeof b == "number") {
        alert(a * b);
    } else if (typeof a == "string" && typeof b == "string") {
        alert(a + b);
    } else {
        alert("输入错啦");
    }
}

myfun8(3, 4); // 输出12;
myfun8("hi,", "你好");//输出hi,你好;
myfun8("hi", 5);//输入错啦.