JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" class="check" value="Check">
    <input type="text" name="user" id="user" class="user" value="">

JavaScript

$(document).ready(function(){
   
    $(".check").click(function(){
    
        if (!$('input.user').val()){
           // DO SOMETHING
           alert ('Empty');
        }else{
            alert("The contents are: " + $('input.user').val());   
        }
        
    });
    
});