JSFiddle - React, Tailwind, and code Playground

HTML

<div class="myclass" data-myattribute="1">1</div>
<div class="myclass" data-myattribute="2">2</div>
<div class="myclass" data-myattribute="3">3</div>
<div class="myclass" data-myattribute="4">4</div>

JavaScript

var classname = document.getElementsByClassName("myclass");

var myFunction = function() {
    var attribute = this.getAttribute("data-myattribute");
    alert(attribute);
};

for(var i=0;i<classname.length;i++){
    classname[i].addEventListener('click', myFunction, false);
}