计算可以输入字数 用法
1.第一种

div id="mod_order_remark" style="display:none;">  <div title="#">上海三星数码我友专供</a>        <span value="联系我"/>        </span>     </span>    </div>    <div name="remork"        id="remork" onkeydown='countChar("status","counter");'      onkeyup='countChar("remork","counter",this);'>      </textarea>      <span          id="btnConfirm" value="确定" />        </span>        <span             id="cancelBtn" value="取消" />        </span>      </div>    </div>  </div></div>

<script> function cal() { if(a.value.length>20) { a.value=a.value.slice(0,20); b.value=20; c.value=0; } else { b.value=a.value.length; c.value=20-eval(b.value); } } </script> <textarea id="a" onpropertychange="cal()"></textarea> 已有字数：<input id=b size=5 value="0" disabled> 剩余字数：<input id=c size=5 value="20" disabled><br>