JSFiddle - React, Tailwind, and code Playground

HTML

<div data-start="3"></div>
<div data-start="10"></div>
<div data-start="19"></div>

CSS

div{
    width: 100px;
    height: 100px;
    border: 1px solid red;
}

JavaScript

function redSquare(div){
    console.log(div)
    var self=this;
    self.div=div;
    self.start=parseInt(div.getAttribute("data-start"));
    self.div.addEventListener("click",self.alert, false);     
}

redSquare.prototype.alert= function(){
    var self=this;
        alert(this.start++);
}


var t = document.getElementsByTagName("div"); 
var rs1= new  redSquare(t[0]);     
var rs2= new  redSquare(t[1]);    

var rs3= new  redSquare(t[2]);