Test 'input' event
HTML
<input id="my-text-box" maxlength="10">
<div id="messages" style="white-space:pre;"></div>JavaScript
var input = document.querySelector('#my-text-box');
var messages = document.querySelector('#messages');
input.addEventListener('input', function()
{
messages.textContent += 'input changed to: ' + input.value + '\n';
});