JavaScript中prototype的使用详解

function Machine(ecode, horsepower) {
  this.ecode = ecode;
  this.horsepower = horsepower;
}

function showme() {
  alert(this.name + " " + this.ecode + " " + this.horsepower);
}

var machine = new Machine("code1", 15);
machine.name = "machine1";
machine.showme = showme;
machine.showme();

//机器
function Machine(ecode, horsepower) {
  this.ecode = ecode;
  this.horsepower = horsepower;
}
//特别注意这一句，Machine.prototype是第一次初始化的时候就初始化好的，
//当调用Machine作为构造函数的时候，engine的值不会再改变
Machine.prototype.engine = this.ecode + " " + this.horsepower;
Machine.prototype.showme = function () { alert(this.name + " " + this.ecode + " " + this.horsepower); }

prototype的作用对象与实例访问

var machine = new Machine("code1", 15);
machine.name = "machine1";
machine.showme(); //输出machine1 code1 15。

基于prototype的继承实现

//小汽车
function Car(name, ecode, horsepower) {
  this.name = name;
  //调用父类的构造函数，使得Car的对象有ecode、horsepower属性
  Machine.call(this, ecode, horsepower);
}
//Car的原型指向Machine，使Car对象有Machine原型的任意属性和方法，比如showme
Car.prototype = new Machine();

//新建一个类Car的对象。
var xiali = new Car("xiali", "aaa", 15);
alert(xiali.engine);
xiali.showme();