不绑架输入--document.getElementById("linkage_"+id_type+"_echo").value="";--联动

 <script>

     function w_linkage(id_type)

     {

         var selected = $("#linkage_"+id_type+"_triger").find("option:selected").text();

         switch (selected)

         {

             case 'APA':

                 document.getElementById("linkage_"+id_type+"_echo").readOnly=false;

                 break;

             default :

             case 'AMS':

                 document.getElementById("linkage_"+id_type+"_echo").value="";

                 document.getElementById("linkage_"+id_type+"_echo").readOnly=true;

                 break;

         }

     }

 </script>

                <tr>

                    <td>位置分类： </td>

                    <td    >

                        <select class="form-control linkage_triger " name="page_position"  onclick="w_linkage('add')"  id="linkage_add_triger"  >

                            <option value="2" >APA</option>

                            <option value="1">AMS</option>

                        </select>

                    </td>

                </tr>

                <tr>

                    <td>keyword：</td>

                    <td><input type="text" name="keyword"></td>

                </tr>

                <tr>

                    <td>brand：</td>

                    <td><input type="text" name="brand"></td>

                </tr>

                <tr>

                    <td>adasin：</td>

                    <td><input type="text" name="adasin" placeholder="选AMS时，请跳过" id="linkage_add_echo"></td>

                </tr>

         <tr>

             <td>位置分类： </td>

             <td>

                 <select class="form-control" name="page_position_edit"  onclick="w_linkage('edit')"  id="linkage_edit_triger"  >

                     <option value="2" >APA</option>

                     <option value="1">AMS</option>

                 </select>

             </td>

         </tr>

         <tr>

             <td>keyword：</td>

             <td><input type="text" name="keyword_edit" value="<?= $_GET['keyword']?>"></td>

         </tr>

         <tr>

             <td>brand：</td>

             <td><input type="text" name="brand_edit" value="<?= $_GET['brand']?>"></td>

         </tr>

         <tr>

             <td>adasin：</td>

             <td><input type="text" name="adasin_edit"  placeholder="选AMS时，请跳过"  value="<?= $_GET['adasin']?>" id="linkage_edit_echo"></td>

         </tr>

//readyonly  交互，不绑架输入

// add edit  为同一脚本

问题：

 document.getElementById("linkage_"+id_type+"_echo").innerHTML="";

 document.getElementById("linkage_"+id_type+"_echo").innerText="";

 $("#linkage_"+id_type+"_echo").emprt();;

为什么失效？