This is one way to work inheritance in js. Data variables are separated from functional ones by calls to prototype.

helloWorld.js

a = function(){
    this.v1 = "Hello";
    this.v2 = "World";
}
a.prototype.print=function(){
  alert(this.v1.concat(this.v2))
}

b = function(){
    a.call(this);
    this.v1 = "hey";
}
b.prototype = Object.create(a.prototype);

let myB = new b();
myB.print();