SOURCE

function copy(target) {
    function fn(){}
    fn.prototype = target
    return new fn()
}

function inherit(subClass,superClass) {
    function fn(){}
    fn.prototype = superClass.prototype
    let obj = new fn()
    obj.constructor = subClass
    subClass.prototype = obj 
}
function Father(name,age) {
    this.name = name
    this.age = age
    this.backpage = [1,2,3]
    this.getName = function(){
        console.log(this.name)
    }
}
Father.prototype.getAge = function(){
    console.log(this.age)
}
function Child(name,age,sex) {
    Father.call(this,name,age)
    this.sex = sex
}
inherit(Child,Father)
let father = new Father("大明",40,"男")
let obj = new Child("小明",18,"男")
obj.getName()
obj.getAge()
obj.backpage[1] = 4
console.log(obj.backpage)
delete obj.backpage
console.log(obj.backpage)
console.log(father.backpage)
console.log(obj.__proto__)
console.log(father.__proto__.getAge)