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javascript 建立 class 方式有很多種：

1. 將程式碼放入 function 內

function Dog () {
    this.name = "";
    this.position = 0;
    this.bark = function (){
        alert("wuff");
    };
    this.walk = function(){
        this.position += 1;
        alert("position = "+this.position);
    }
    this.getName = function (){
        return this.name;
    }
}

var dog = new Dog();
dog.name = "Ralph";
dog.bark(); //Popup box with "wuff"
dog.walk(); //Position increases by 1;
alert(dog.getName()); //Outputs dog's name*/

2. 將程式碼放入 object 內

var Dog = {
    name    :   "",
    position:   0,
    bark    :   function(){ alert("wuff") },
    walk    :   function(){
        this.position += 1;
        alert("position = "+this.position);
    },
    getName :   function(){
        return this.name
    }
}
Dog.name = "Ralph";
Dog.bark(); //Popup box with "wuff"
Dog.walk(); //Position increases by 1;
alert(Dog.getName()); //Outputs dog's name

3. 使用 prototype 建立 class

function Dog (){}
Dog.prototype.name = "";<
Dog.prototype.position = 0;
Dog.prototype.bark = function (){
    alert("wuff");
}
Dog.prototype.walk = function (){
    this.position += 1;
    alert("position = "+this.position);
}
Dog.prototype.getName = function(){
    return this.name;
}

var dog = new Dog();
dog.name = "Ralph";
dog.bark(); //Popup box with "wuff"
dog.walk(); //Position increases by 1;
alert(dog.getName()); //Outputs dog's name


// Here is a Puppy class to show how inheritance is done
// It inherits all the methods of the Dog class, but overwrites the bark method for a more puppy like bark
function Puppy (){}
Puppy.prototype = new Dog();
Puppy.prototype.bark = function (){
    alert("Yelp");
}
var puppy = new Puppy();
puppy.name = "Ralph";
puppy.bark(); //Popup box with "Yelp"
puppy.walk(); //Position increases by 1;
alert(puppy.getName()); //Outputs puppy's name

文章參考來源：http://www.devirtuoso.com/2009/09/object-oriented-programming-with-javascript/