JSFiddle - React, Tailwind, and code Playground

HTML

<div id="Day">1Day</div>

CSS

#Day{
 border: outset;
 padding: 2px;
 display: inline-block;
 cursor: pointer;
 border-radius: 4px;
}
#Day:hover{
 border: inset;
}

JavaScript

var theElement = document.getElementById("Day");
    theElement.onclick = function(){
     alert("Hi");
    };