JS 提示输入字符数

<script type="text/javascript">function checkLength(which) {var maxChars = 250;if (which.value.length > maxChars)which.value = which.value.substring(0,maxChars);var curr = maxChars - which.value.length;document.getElementById("chLeft").innerHTML = curr.toString();}</script>

 <table>   <tr>   <td>   <textarea name="description" onkeyup="checkLength(this);"></textarea><br /><small><font color="red">文字最大长度: 100. 还剩:</font><font color="blue"> <span id="chLeft">100</span>.</font></small>   </td>   </tr>   </table>