JS 混合构造函数 和 动态原型

混合构造函数,  就是 原型模式+普通构造函数方式

构造函数 定义对象的非函数属性.

原型方式  定义 对象的函数属性(方法)

function Car(sColor,iDoors,iMpg) {
  this.color = sColor;
  this.doors = iDoors;
  this.mpg = iMpg;
  this.drivers = new Array("Mike","John");
}

Car.prototype.showColor = function() {
  alert(this.color);
};

var oCar1 = new Car("red",4,23);
var oCar2 = new Car("blue",3,25);

oCar1.drivers.push("Bill");

alert(oCar1.drivers);    //输出 "Mike,John,Bill"
alert(oCar2.drivers);    //输出 "Mike,John"

下面说下动态原型:

function Car(sColor,iDoors,iMpg) {
  this.color = sColor;
  this.doors = iDoors;
  this.mpg = iMpg;
  this.drivers = new Array("Mike","John");
  
  if (typeof Car._initialized == "undefined") {
    Car.prototype.showColor = function() {
      alert(this.color);
    };
    
    Car._initialized = true;
  }
}

不管实例化多少个 car对象,那么 showColor函数 只初始化一次.