costom extend

//自定義繼承

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var rect = function() {
};

myextend(rect, Object, {
            width : 5,
            height : 6
        });
rect.prototype.area = function() {
    alert("this is RectAngle.prototype.area() method");
    return this.width * this.height;
};

//alert(rect.width);
//alert(rect.height);
//alert(rect.area());


var rect_01 = function() {
};

myextend(rect_01, rect, {
            width : 2,
            height : 3
        });

//alert(rect_01.height);
//alert(rect_01.width);
alert(rect_01.area());

 

 

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//  多對象順序繼承時

 

function myextend(child, father, override) {
    child.prototype = father.prototype;
    for (var item in override) {
        child.prototype[item] = override[item];
    }
}

RectAngle = function() {
};
myextend(RectAngle, Object, {
            width : 10,
            height : 20
        });

//RectAngle.prototype = {
//    area : function() {
//        alert("this is RectAngle.prototype.area() method");
//        return width * height;
//    }
//};

 

/* 如以上定義成員方法時，在子類中訪問不到的 */

RectAngle.prototype.area = function() {
    alert("this is RectAngle.prototype.area() method");
    return this.width * this.height;
}

alert(RectAngle.width);
alert(RectAngle.height);
alert(RectAngle.area());

var Rect = function() {
};

myextend(Rect, RectAngle, {
            width : 3,
            height : 5
        });

alert(Rect.width);
alert(Rect.height);
alert(RectAngle.area());
alert(RectAngle.width);
alert(RectAngle.height);
alert(Rect.area());

 

/* 以上測試中發現：Rect 和 RectAngle 共用prototype 中的屬性 */