how to create a function like something.function() in JavaScript?

Question

Imagine I have this function:

function test(firstNumber,SecondNumber){
  return (firstNumber*secondNumber);
}

I want to do the same function (the above function) in a different way like bellow and I want to know how is it possible in JavaScript:

var firstNumber= 10; //some number;
firstNumber.test(secondNumber);

Answer 1

You could use a custom prototype of Number for it.

Number.prototype.test = function (n) {
    return this * n;
}

var firstNumber = 10; //some number;
document.write(firstNumber.test(15));

Answer 2

You can extend the Number object with your own functions.

Number.prototype.test = function (other) {
    return this.valueOf() * other;
};

var firstNumber = 10;
var secondNumber = 10;

firstNumber.test(secondNumber);

Please keep in mind that extending native Javascript objects is a bad practice.

Answer 3

Just some other way instead of extending native javascript objects

var utils = {
  add: function(a, b) {
   return (a + b)
  }
}

var one = 1
var two = 2

utils.add(1, 2) // prints 3