JSFiddle - React, Tailwind, and code Playground

HTML

<p>Random number : <span id="rdn_no"></span></p>
<p id="numbers"></p>
<button id="generate">
  Next Random number
</button>

JavaScript

var alreadyArr = new Array();
$(function() {
  $("#generate").click(function() {
    var newFound = false;
    var num;
    do {
      num = (Math.floor(Math.random() * 12) + 1) * 30;
      if (alreadyArr.length == 12) {
        alreadyArr = [num];
        newFound = true;
      } else if (alreadyArr.indexOf(num) < 0) {
        alreadyArr.push(num);
        newFound = true;
      }
    } while (!newFound);
    $("#rdn_no").text(num);
    $("#numbers").text(alreadyArr);
  });
});