ES5 prototype
function Dog(name){
this.name = name
this.legs = 4
}
Dog.prototype.say = function(){
console.log(`${this.name} - ${this.legs}`)
}
Dog.prototype.kind = '狗'
const d1 = new Dog('tom')
const d2 = new Dog('jimmy')
d1.say()
d2.say()
在prototype中放置可共享的属性（避免内存浪费），在函数中放置各自的私有属性
ES6 class
class Dog {
kind = '狗'
constructor(name){
this.name = name
this.legs = 4
}
say(){
}
run(){
}
}
const d1 = new Dog('jimmy')
d1.say()
js原型链继承的实现
function Animal(legsNumber){
this.legsNumber = legsNumber
}
Animal.prototype.kind = '动物'
function Dog(name){
Animal.call(this,4) // this.legsNumber = 4
this.name = name
}
// Dog.prototype.__proto__ = Animal.prototype 不是所有浏览器都存在__proto__属性
var emptyAnimal = function(){}
emptyAnimal.prototype = Animal.prototype
Dog.prototype = new emptyAnimal()
Dog.prototype.say = function(){
console.log(`${this.name} - ${this.legs}`)
}
Dog.prototype.kind = '狗'
new的作用：
- 创建临时对象
- this = 临时对象
- 'this.proto' = 构造函数的prototype
- 执行构造函数
- return this
我们希望执行上面的1，2，3，5，因为4在我们声明Dog时已经使用，所以我们需要构建一个空的函数体的emptyAnimal，然后我们执行Dog.prototype = new emptyAnimal()就能完成继承
es6 class 继承
class Animal {
constructor(legsNumber){
this.legsNumber = legsNumber
}
run(){}
}
class Dog extends Animal{
constructor(name){
super(4)
this.name = name
}
say(){
console.log(`${this.name} ${this.legsNumber}`)
}
}
