JavaScript物件導向編程（8）使用中間函數，javascript物件導向
上一講我們提出一個很好的思路，將一個類的可複用部分全部定義在prototype中，這樣子類繼承的時候可以很方便地通過prototype來繼承；
但是也帶來一個問題就是子類在重寫prototype中的屬性時會改變所有執行個體的屬性，這是因為父類和子類執行個體都共用同一個prototype；
怎麼解決呢？思路就是利用一個中間函數，具體請看代碼：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>臨時函數F</title></head><body><script type="text/javascript">function Shape(){}Shape.prototype.name = 'shape';Shape.prototype.toString = function() {return this.name;};function TwoDShape(){}//用中間函數先繼承基類var F = function(){}F.prototype=Shape.prototype;//子類繼承中間函數TwoDShape.prototype = new F();TwoDShape.prototype.constructor = TwoDShape;//這是真正的重寫TwoDShape.prototype.name = '2D shape';function Triangle(side, height) {this.side = side;this.height = height;this.getArea = function(){return this.side * this.height / 2;};}var F = function(){}F.prototype=TwoDShape.prototype;Triangle.prototype = new F();Triangle.prototype.constructor = Triangle;//重寫Triangle.prototype.name="Triangle";var my = new Triangle(5, 10);/*alert(my.getArea());alert(my.toString());//自己沒有toString方法，繼承而來alert(my.constructor);alert(my instanceof TwoDShape);//有繼承的特性alert(my instanceof Shape);*/alert(my.name);var shape = new Shape();alert(shape.name);//正常了</script></body></html>
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