你不知道的JS-读书笔记（四）--混合对象类

寄生继承

//“传统的 JavaScript 类” Vehicle
function Vehicle() {
this.ehgines = 1;
}
Vehicle.prototype.ignition = function() {
console.log( "Turning on my engine." );
};
Vehicle.prototype.drive = function() {
this.ignition();
console.log( "Steering and moving forward!" );
};

//“寄生类” Car
function Car() {
// 首先， car 是一个 Vehicle
var car = new Vehicle();
// 接着我们对 car 进行定制
car.wheels = 4;

// 保存到 Vehicle::drive() 的特殊引用
var vehDrive = car.drive;

// 重写 Vehicle::drive()
car.drive = function() {
vehDrive.call( this );
console.log("Rolling on all " + this.wheels + " wheels!"
);
return car;
}
var myCar = new Car(); // var myCay = Car(); 更好，避免创建并丢弃多余的对象
myCar.drive()
// "Turning on my engine."
// "Steering and moving forward!"
// "Rolling on all 4 wheels!"

小结