JSFiddle - React, Tailwind, and code Playground

JavaScript

//Add a property to the instance
var date = new Date(); 
date.newProp = 'test'; 
alert(date.newProp); //test

//vs

//Add a property to all instances existing 
//and too be created
Date.prototype.newProp2 = 'new prop'; 

var date2 = new Date(); 
alert(date2.newProp);//undefined 
alert(date2.newProp2); //new prop

//See how the prototype modified the existing instance as well. 
alert(date.newProp2); //new  prop