javascript学习笔记(十) js对象 继承

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//定义 SuperClass类，有一个属性property和一个方法getSuperValue
function SuperClass() {
this.property = true;
}
SuperClass.prototype.getSuperValue = function() {
return this.property;
}

//定义SubClass类，有一个属性subproperty和后来添加的一个方法getSubValue
function SubClass() {
this.subproperty = false;
}

//SubClass类继承SuperClass类
SubClass.prototype = new SuperClass();

//SubClass类添加一个方法getSubValue
SubClass.prototype.getSubValue = function() {
return this.subproperty;
}

//创建SubClass类的实例
var instance = new SubClass();
alert(instance.getSuperValue());

alert(instance instanceof Object); //true ，instance是Object的实例吗?
alert(instance instanceof SuperClass); //true ，instance是SuperClass的实例吗?
alert(instance instanceof SubClass); //true，instance是SubClass的实例吗?

alert(Object.prototype.isPrototypeOf(instance)); //true
alert(SuperClass.prototype.isPrototypeOf(instance)); //true
alert(SubClass.prototype.isPrototypeOf(instance)); //true

View Code
function SuperClass() {
this.property = true;
}
SuperClass.prototype.getSuperValue = function() {
return this.property;
}

function SubClass() {
this.subproperty = false;
}

//SubClass继承SuperClass
SubClass.prototype = new SuperClass(); //这个要先写，新添加的方法和重写超类的方法要写在后面，否则重写的超类方法将永远无法调用

//添加新方法
SubClass.prototype.getSubValue = function() {
return this.subproperty;
}
//重写超类的方法
SubClass.prototype.getSuperValue = function() {
return false;
}
var instance = new SubClass();
alert(instance.getSuperValue()); //fales,这里SubClass的实例调用了SubClass的getSuperValue()方法，而屏蔽了SuperClass的getSuperValue()方法，
//使用SuperClass的方法会调用SuperClass的getSuperValue()方法

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function SuperClass(name) {
this.name = name;
}
function SubClass(){
SuperClass.call(this,"RuiLiang"); //继承了SuperClass,同时向SuperClass传递了参数
this.age = 29; //实例属性
}

var instance = new SubClass();
alert(instance.name); //RuiLiang
alert(instance.age); //29

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//创建SuperClass
function SuperClass(name) {
this.name = name;
this.colors = ["red","blue","green"];
}
SuperClass.prototype.sayName = function() {
alert(this.name);
}

////创建SubClass
function SubClass(name,age) {
SuperClass.call(this,name); //继承属性
this.age = age; //自己的属性
}

SubClass.prototype = new SuperClass(); //继承方法
SubClass.prototype.sayAge = function() { //SubClass添加新方法
alert(this.age);
};

//使用
var instance1 = new SubClass("RuiLiang",30);
instance1.colors.push("black");
alert(instance1.colors); //"red,blue,green,black"
instance1.sayName(); //"RuiLiang"
instance1.sayAge(); //30

var instance2 = new SubClass("XuZuNan",26);
alert(instance2.colors); //"red,blue,green"
instance2.sayName(); //"RuiLiang"
instance2.sayAge(); //30