[devote]

<script type="text/javascript" src="http://devote.github.io/files/letjs/let.js"></script>
<script type="text/javascript">
  letJS.setHandler("data-let-pattern", function(rules) {
    var elem = document.querySelector(rules.rule);
    var value = elem && +(elem.value || elem.textContent || elem.innerHTML);
    return !elem || +rules.expectedValue <= value;
  });
</script>

<div id="count">44</div>
<input type="text" data-let-pattern="#count" />

<br/><button onclick="var a = +prompt('Введи число'); document.querySelector('#count').innerHTML=a;">Изменить паттерн</button>