The_example
This is a very simple example showing you how to do a live demo in MDN. For more information, see Live samples.
<form>
<label>Try me<input type="text" name="name"></label>
<input type="submit" value="go">
</form>
form {
border-radius: 10px;
background: powderblue;
}
var f = document.querySelector('form');
f.addEventListener('submit', function(ev) {
ev.preventDefault();
document.querySelectorAll('input')[1].value = 'sending';
}, false);