<html>
<head>
<meta charset="utf8">
</head>
<body>
<table id="table">
<tr>
<td>Аа</td>
<td>Бб</td>
<td>Yy</td>
<td>Гг</td>
<td>Дд</td>
<td>Hh</td>
</tr>
<tr>
<td>Оо</td>
<td>Gg</td>
<td>Пп</td>
<td>Рр</td>
<td>Сс</td>
<td>Тт</td>
</tr>
</table>
<script>
f=function(){if(/\w+/.test(this.innerHTML)) this.style.background="red"}
;[].forEach.call(document.querySelectorAll("table td"), function(el){el.onclick=f})
</script>
</body>
</html>