【笔记】javascript原型链继承实例

来源：互联网发布：mac shell脚本编写编辑：程序博客网时间：2024/06/15 02:57

function Shape(){ this.name = 'shape'; this.toString = function(){  return this.name; }}function TwoDShape(){ this.name = '2D shape';}function Triangle(side,height){ this.name = 'Triangle'; this.side = side; this.height = height; this.getArea = function(){  return this.side*this.height/2; };}/* inheritance */TwoDShape.prototype = new Shape();Triangle.prototype = new TwoDShape();

当我们对对象的prototype属性进行完全重写时，有时候会对对象constructor属性产生一定的负面影响。

所以，在我们完成相关的继承关系设定后，对这些对象的const属性进行相应的重置是一个非常好的习惯。

TwoDShape.prototype.constructor = TwoDShape;Triangle.prototype.constructor = Triangle;

改写：

<span style="font-family:Microsoft YaHei;font-size:14px;color:#333333;">function Shape(){}Shape.prototype.name = 'shape';Shape.prototype.toString = function(){ return this.name;}function TwoDShape(){}TwoDShape.prototype = new Shape();TwoDShape.prototype.constructor = TwoDShape;TwoDShape.prototype.name = '2d shape';function Triangle(side,height){ this.side = side; this.height = height;}Triangle.prototype = new TwoDShape;Triangle.prototype.constructor = Triangle;Triangle.prototype.name = 'Triangle';Triangle.prototype.getArea = function(){ return this.side*this.height/2;}</span>

再改写（引用传递而不是值传递）：

<span style="font-size:14px;color:#333333;">function Shape(){}Shape.prototype.name = 'shape';Shape.prototype.toString = function(){ return this.name;}function TwoDShape(){}TwoDShape.prototype = Shape.prototype;TwoDShape.prototype.constructor = TwoDShape;TwoDShape.prototype.name = '2d shape';function Triangle(side,height){ this.side = side; this.height = height;}Triangle.prototype = TwoDShape.prototype;Triangle.prototype.constructor = Triangle;Triangle.prototype.name = 'Triangle';Triangle.prototype.getArea = function(){ return this.side*this.height/2;}</span>

虽然提高了效率，但是这样的方法有个副作用，因为是引用传递，而不是值传递，所以“父对象”中的name值受到了影响。

子对象和父对象指向的是同一个对象。所以一旦子对象对齐原型进行修改，父对象也会随即被改变。

再再改写（使用临时构造器）：

<span style="font-size:14px;color:#333333;">function Shape(){}Shape.prototype.name = 'shape';Shape.prototype.toString = function(){ return this.name;}function TwoDShape(){}var F = function(){}F.prototype = Shape.prototype;TwoDShape.prototype = new F();TwoDShape.prototype.constructor = TwoDShape;TwoDShape.prototype.name = '2d shape';function Triangle(side,height){ this.side = side; this.height = height;}F.prototype = TwoDShape.prototype;Triangle.prototype = new F();Triangle.prototype.constructor = Triangle;Triangle.prototype.name = 'Triangle';Triangle.prototype.getArea = function(){ return this.side*this.height/2;}</span>

虽然提高了效率，但是这样的方法有个副作用，因为是引用传递，而不是值传递，所以“父对象”中的name值受到了影响。

子对象和父对象指向的是同一个对象。所以一旦子对象对齐原型进行修改，父对象也会随即被改变。

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