JSFiddle - React, Tailwind, and code Playground

HTML

<form action="http://appid.appspot.com/api/foo" id="contact-form" method="post"
name="contact-form" onsubmit="return doStuff() ? true:false;">
    <fieldset>
        <input name="email" value="Email"
             onblur="if(this.value===''){this.value=this.defaultValue}" 
            onfocus="if(this.value===this.defaultValue){this.value=''}" > <br>
        <input name="subject" value="Subject"
             onblur="if(this.value===''){this.value=this.defaultValue}" 
            onfocus="if(this.value===this.defaultValue){this.value=''}" > <br>
        <textarea name="message" 
                onblur="if(this.value===''){this.value=this.defaultValue}" 
               onfocus="if(this.value===this.defaultValue){this.value=''}"
                      >Message</textarea>

        <div class="buttons">
            <a href="#" onclick=
            "document.getElementById('contact-form').reset()">Clear</a>
            <a href="#" onclick=
            "if(doStuff()){document.getElementById('contact-form').submit();}">Send</a>
        </div>
    </fieldset>
</form>

JavaScript

function doStuff(){
    var eml=document.getElementsByName('email')[0].value;
        msg=document.getElementsByName('message')[0];
    msg.value = 'Email: ' + eml + ' Message: ' + msg.value;
    alert ('message has been submitted');
    return true;
}