javascript - 如何在 javascript 中扩充父类(super class)中的方法

Question

我在基类中有一个方法，我想将其保留在子类中，但只需将其添加即可。我发现了很多关于使用属性和方法扩充类和对象的东西，但我找不到，或者不明白，如何扩充方法。最坏的情况是我必须将父类的整个方法粘贴到子类中，但这似乎是重复代码......请帮忙

function someObject (){
    this.someProperty = 1;
    this.incrementProperty = function incrementProperty(){   
        this.propertyOfSomeObject += 1;
    }
}

function newObject (){
    someObject.call(this);
    this.incrementProperty =  function incrementProperty(){
        //do everything the super class has for this property already
        return this.someProperty;
    }
}

var incrementer = new newObject;
alert (incrementer.incrementProperty()); //I want output to be 2

Answer 1

// parent object
function someObject () {
    this.someProperty = 1;
}

// add incrementProperty to the prototype so you're not creating a new function
// every time you instantiate the object
someObject.prototype.incrementProperty = function() {   
  this.someProperty += 1;
  return this.someProperty;
}

// child object
function newObject () {
    // we could do useful work here
}

// setup new object as a child class of someObject
newObject.prototype = new someObject();
// this allows us to use "parent" to call someObject's functions
newObject.prototype.parent = someObject.prototype;
// make sure the constructor points to the right place (not someObject)
newObject.constructor = newObject;

newObject.prototype.incrementProperty = function() {
    // do everything the super class has for this property already
    this.parent.incrementProperty.call(this);
    return this.someProperty;
}

var incrementer = new newObject();
alert (incrementer.incrementProperty()); // I want output to be 2

参见:http://jsfiddle.net/J7RhA/