JSFiddle - React, Tailwind, and code Playground

HTML

<form id="message_form" method="post">
                <div class="success">Contact form submitted! <strong><br>We will be in touch soon.</strong></div>
                <fieldset>
                    <label class="name"><span class="formlabel">  Name:</span>
                        <input type="text" name="name" id="name" placeholder="Please provide your full name">
                        <span class="error">*This is not a valid name.</span>
                        <span class="empty">*This field is required.</span>
                        <span class="clear"></span>
                    </label>
                    <label class="phone"><span class="formlabel">Phone:</span>
                        <input type="text" name="phone" id="phone" placeholder="Example: (555) 555-5555">
                        <span class="error">*This is not a valid phone number.</span>
                        <span class="empty">*This field is required.</span>
                        <span class="clear"></span>
                    </label>
                    <label class="email"><span class="formlabel">Email:</span>
                        <input type="text" name="email" id="email" placeholder="Please provide your email address" >
                        <span class="error">*This is not a valid email address.</span>
                        <span class="empty">*This field is required.</span>
                        <span class="clear"></span>
                    </label>
                    <span class="formlabel_message">Message:</span>
                    <label class="message">
                        <textarea name="message" id="message" placeholder="Please enter your message here" style="margin-top:0;"></textarea>
                        <span class="error">*The message is too short.</span>
                        <span class="empty">*This field is required.</span>
                        <span class="clear"></span>
                    </label>
                    <div...

JavaScript

$(function(){
    $('#message_form #submit').attr('disabled', 'disabled');  
    $('#message_form input,textarea').on('keyup', function(){
        if($('#name').val() && $('#phone').val() && $('#email').val() && $('#message').val()){
             $('#message_form #submit').removeAttr("disabled");           
        }
        else{
           $('#message_form #submit').attr('disabled', 'disabled');
        }
    });
});