限制输入字数JS

    <tr>
            <th><b>说明内容：</b><span id="content">(500字以内)</span></th>
        </tr>
        <tr>
            <td><input type="text" name="content" value="{$data['content']}"  class="easyui-textbox" data-options="required:false,multiline:true" style="width:700px; height:350px;"></td>
        </tr>

        <script type="text/javascript">
                $("input[name=content]").textbox({
                 onChange:function(newValue,oldValue){
                     if(newValue.length>5){
                     // $(".easyui-linkbutton").attr('disabled','false');//禁用a标签中的onclick事件
                       // $('.easyui-linkbutton').removeAttr('onclick');//去掉a标签中的onclick事件
                       $("span#content").html('输入的内容已超过5字！');
                       $("span#content").css('color','red');
                     }else{
                         $("span#content").html('');
                      return newValue;

                       }
                     }
                })
        </script>

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<tr>
        <td>
        <b>说明内容：</b>
            <span>（限500字以内，您还可以输入字数：<input name="termLen" value="500" style=" font-size:15pt; color:red; border:0; text-align:center; width: 40px"  readonly />字）</span>
        </td>
    </tr>

    <tr>
        <td colspan="2" align="center">
            <textarea id="content" name="content" style="width: 90%; height: 300px; margin-top:5px;" onKeyPress="checkLen(this)" onKeyUp="checkLen(this)" onChange="checkLen(this)">{$data['content']}</textarea>
        </td>
    </tr> 

    <script type="text/javascript">
            function checkLen(term){
                document.all.termLen.value=500-term.value.length;
                    if (document.all.termLen.value<=0){
                            term.value=term.value.substring(0,500);
                        }
             }
    </script>    

    <tr>
        <th style="text-align:center;"><a class="easyui-linkbutton" href="JavaScript:void(0);" onclick="From_Submit('PointsSign')" data-options="iconCls:'iconfont icon-add'"><span style="font-size:14px; font-weight:600;">保存</span></a></th>
    </tr>