类的四种定义方法
1.工厂模式
function Car(name, color, price) {
var tempcar = new Object;
tempcar.name = name;
tempcar.color = color;
tempcar.price = price;
tempcar.getCarInfo = function () {
console.log(`name: ${this.name},color: ${this.color},price: ${this.price}`);
}
return tempcar;
}
var mycar = new Car('BMW', 'red', '100000');
mycar.getCarInfo();
缺点:每次 new 一个对象的时候,都会重新创建一个 getCaeInfo() 函数;
2. 构造函数方式
function Car(name, color, price) {
this.name = name;
this.color = color;
this.price = price;
this.getCarInfo = function () {
console.log(`name: ${this.name},color: ${this.color},price: ${this.price}`);
}
}
var myCar = new Car('桑塔纳', 'green', '123456');
myCar.getCarInfo();
优点:
-
不用创建临时对象;
-
不用返回临时对象;
缺点:与‘工厂模式’相同,重复创建函数;
3.原型方式
function Car(name, color, price) {
Car.prototype.name = name;
Car.prototype.color = color;
Car.prototype.price = price;
Car.prototype.getCarInfo = function () {
console.log(`name: ${this.name},color: ${this.color},price: ${this.price}`);
}
}
var myCar = new Car('兰博基尼', 'red', '10000000000');
myCar.getCarInfo();
优点:
-
解决了重复创建函数的问题;
-
可以使用 instanceof 检验类型 myCar instanceof Car // true
缺点: 多个实例创建的相同属性指向同一块内存;
例子:
Car.prototype.drivers = ['Tim', 'Jone'];
myCar.drivers.push('mike');
console.log(myCar.drivers); // ['Tim', 'Jone', 'mike']
4.动态原型方式(推荐)
function Car(name, color, price, drivers) {
this.name = name;
this.color = color;
this.price = price;
this.drivers = drivers;
}
Car.prototype.getCarInfo = function () {
console.log(`name: ${this.name},color: ${this.color},price: ${this.price}`);
}
var myCar = new Car('兰博基尼', 'red', '10000000000', ['qaz', 'wsx']);
myCar.drivers.push('mi');
console.log(myCar.drivers); // ["qaz", "wsx", "mi"]
var myCar1 = new Car('兰博基尼1', 'red1', '100000000001', ['qaz1', 'wsx1']);
myCar1.drivers.push('mi1');
console.log(myCar1.drivers); // ["qaz1", "wsx1", "mi1"]
思想:
类的属性 要随实例对象动态改变; => 动态
类的方法 要随原型保持不变;=> 原型