JSFiddle - React, Tailwind, and code Playground

JavaScript

function A() {
    var numbers = [];

    this.addNumber = function(number) {
        numbers.push(number);
    }

    this.getNumbers = function() {
        return numbers;
    }
}

A.prototype.alertNumbers = function() {
    var numbers = this.getNumbers();
    var length = numbers.length;
    var number;
    var numbersString = "";
    for (var i = 0; i < length; i++) {
        number = numbers[i];
        numbersString += " " + number;
    }
    alert(numbersString);
}

B.prototype = new A();

function B() {
    this.addNumber(1);
    this.addNumber(2);
}

var b = new B();
b.alertNumbers();

var otherB = new B();
otherB.alertNumbers();