JSFiddle - React, Tailwind, and code Playground

HTML

<form action="" method="post" >
    <input type="text" name="uName" id="uName" />
    <input type="password" name="passKey" id="passKey" />
    <inpu type="submit" id="submit"/>
</form>

JavaScript

$('#submit').click(function(){
    if( $('#uName').val() == ''){
        alert('empty');
    }
});