js继承方式

1、原型链继承

function One (){
  this.number = 1
  this.arr = ['A']
}

Son.prototype = new One()

function Son(){

}

const son1 = new Son()
const son2 = new Son()

son1.number = 2
son1.arr.push('B')

console.log(son1.number) // 2
console.log(son2.arr) // [ 'A', 'B' ]

console.log(son2.number) // 1
console.log(son2.arr) // [ 'A', 'B' ]

缺点：复合类型数据改变会影响所有子函数
2、构造函数继承

function One (){
  this.arr = ['A']
  this.fn = function(){
    // ...
  }
}
function Son(){
  One.call(this)
}

const son1 = new Son()
const son2 = new Son()

son1.arr.push('B')

console.log(son1.arr) // [ 'A', 'B' ]
console.log(son2.arr) // [ 'A' ]
console.log(son1.fn === son2.fn) // false

缺点：如果属性有公用函数，重复多了会浪费内存
3、组合继承
顾名思义，也就是以上两种方式的综合

function One(){
  this.number = 1
  this.arr = []
}

One.prototype.fn = function(){
  // ...
}

function Two(){
  One.call(this)
}

const son1 = new Two()
const son2 = new Two()

son1.number ++
son1.arr.push(1)

console.log({...son1})
console.log({...son2})