请用js实现下面问题

Question

用js实现一个类P 包含成员变量a，成员变量b成员函数sum sum输出a与b的和,a,b默认值都为0.实现一个类M,M继承自P,在P的基础上增加成员变量c成员变量函数sum变成a,b,c的和

Answer 1

    class P{
        constructor() {
            this.a = 0;
            this.b = 0;
            this.sum = function(){
                console.log(this.a+this.b);
                return this.a+this.b
            }
        }
        
    }
    class M extends P{
        constructor(a, b) {
            super(a, b ); // 调用父类的constructor(a,b)
            this.c = 0;
            this.sum = function(){
                console.log(this.a+this.b+this.c);
                return this.a+this.b+this.c
            }
        }
        
    }
    var p = new P()
    console.log(p)
    p.sum();
    var m = new M()
    console.log(m)
    m.sum()

Answer 2

function P(a,b){
    this.a = a || 0;
    this.b = b || 0;
}
P.prototype.sum = function() { return this.a + this.b;}
function M(a,b,c){
    P.call(this,a,b);
    this.c = c || 0;
}
M.prototype = new P();
M.prototype.constructor = M;
M.prototype.sum = function() { return this.a + this.b + this.c;}

p = new P(1,2);
m = new M(1,2,3);
p.sum();// 3
m.sum(); //6

Answer 3

class P {
    a = 0
    b = 0
    sum(){
        return this.a+this.b
    }
    constructor(){
    
    } 
}

class M extends P {
    c
    sum(){
        return super.sum() + this.c
    }
    
    constructor(){
        super()
    } 
}

let p = new P()
p.a = 10
p.b = 1
console.log(p.sum())

let m = new M()
m.a = 1
m.c = 11
console.log(m.sum())