javascript - Newbie asking for help: Why does Console.log here return undefined?

Question

function d(){this.get=function(){this.getNum()}};
d.prototype.getName=function(){return 3;} ;
var d = new d();
console.log(d.get());//undefined

Why is undefined shown here? Instead of 3? Please answer

Answer 1

function d(){this.get=function(){return this.getName()}};
d.prototype.getName=function(){return 3;};
var d = new d();
console.log(d.get());//undefined

Answer 2

function d(){this.get=function(){return this.getNum()}};

What do you say

Answer 3

function d(){this.get=function(){return this.getName();}};
d.prototype.getName=function(){return 3;};
var d = new d();
console.log(d.get());

Compare for yourself

Answer 4

num name

Answer 5

this.getnum is changed to this.getname

Answer 6

function d(){
            this.get= function(){
                return this.getName()
            }
        };
        d.prototype.getName = function(){
            return 3;
        };
        var d = new d();
        console.log(d.get());