JSFiddle - React, Tailwind, and code Playground

HTML

<form action="#">
    <input type="text" name="email" id="email" />
    <input type="submit" name="btn_submit" id="btn_submit" value="Submit" disabled="disabled">
</form>

JavaScript

$(document).ready(function(){
    $('#email').keyup(function(){
        var regexp = /^\w+[@]\w+\.\w{2,4}$/;
        if(regexp.test($(this).val())){
            $("#btn_submit").prop('disabled', false);
        }
        else $("#btn_submit").prop('disabled', true);
            
    });
});