JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" class="btnsubmit" id="test"/>
<input type="button" value="submit" id="btnsubmit"/>

JavaScript

$(".btnsubmit").keypress(function() 
{ 
    if($('input#test').val()==="" || $.isNumeric($('input#test').val()))
    {
      alert("error");
    }
});