JSFiddle - React, Tailwind, and code Playground

HTML

it restricts instantiation of a class to a single object
 In the event of an instance already existing, it simply returns a reference to that object.

JavaScript

var mySingleton = (function () {
    var instance;
  function init() {
       var someObj = {};
      var rand = Math.random();      
      someObj.getRandomNumber=function() {
        return rand;
      } 
      return someObj;
 };
  return {
    getInstance: function () {
  //  if ( !instance ) {
      instance = init();
     //   return instance;
  //  }
        return instance;

 }
  };     
})();

var singleA = mySingleton.getInstance();
var singleB = mySingleton.getInstance();
console.log(singleA.getRandomNumber())
console.log(singleB.getRandomNumber())
if( singleA.getRandomNumber() == singleB.getRandomNumber() ){
alert("true")
}// true