Javascript new array prototype in new object constructor

Question

If I do:

Array.prototype.test = "test"
Array.prototype.t = function() {return "hello"}

Every new Array will have the property test and the method t.

How can I do the same without affecting all Arrays?

Like:

Names = function(arr){
  // Contacts constructor must be the same of Array 
  // but add the property test and the function t
}
z=new Names(["john","andrew"])

So that z.test will return "test" and z.t() will return "hello"? (but Array.test and Array.t would stay undefined)

I explain better:

Array.prototype.t="test";
Array.prototype.test = function(){ return "hello";}

z=new Array("john", "andrew")
console.log(z);

But this affects ALL arrays. I want the same but with a new constructor Names that inherits Array constructor.

Answer 1

class Names extends Array {
  constructor(...args) {
    super(...args);
  }
}

Names.prototype.t = 'test';

let z = new Names("john", "andrew")
z.push('Amanda')

console.log(z.t)
console.log(z)

You can easily set it at Names.prototype