javascript - 根据选择启用/禁用输入框

Question

我希望在从选择下拉列表中选择特定值时启用此文本框，并在选择任何其他选项时禁用此文本框。

这是我的 html:

<select name="status" id ="combo">
      <option value="_">Please choose..</option>
        <option  value="Pending">Pending</option>
        <option  value="Process">Process</option>
        <option  value="Delivered" >Delivered</option>
      </select>
 <tr valign="baseline">
 <td nowrap="nowrap" align="right" class="postage" >Postage:</td>
 <input type="text" name="postage" id="textbox" >

Answer 1

试试这个:

var select_element = document.getElementById( "combo" );
var selected = select_element.options[ select_element.selectedIndex ].value

if(selected == "Delivered"){
  document.getElementById("textbox").disabled = false;
}else{
  document.getElementById("textbox").disabled = true;
}