Turn on / off the dropdown list based on another dropdown list

Question

I have two dropdowns

<select id="servergroup" multiple="multiple">             
  <option value="P1">P1</option>
  <option value="P2">P2</option>
  <option value="P3">P3</option>
  <option value="P4">P4</option>
</select>

<select id="servername" multiple="multiple">
  <option value="s597ap233">s597ap233</option>
  <option value="s597dp392">s597dp392</option>
  <option value="s397dp095">s397dp095</option> 
</select>

I want the second drop-down list to be included only if we select a value in the first drop-down list. It should turn off again if we deselect the first drop-down list. Can I find out how this can be achieved with jQuery?

Answer 1

You can use the attribute disabledand use JavaScript, you can set it as falseortrue

function check(){
  if(document.getElementById('servergroup').value!='')
    document.getElementById('servername').disabled=false;
  else
    document.getElementById('servername').disabled=true;
}

<select onchange="check()" id="servergroup" multiple="multiple">

    <option value="P1">P1</option>
    <option value="P2">P2</option>
    <option value="P3">P3</option>
    <option value="P4">P4</option>
    </select>
    <select disabled id="servername" multiple="multiple">
    <option value="s597ap233">s597ap233</option>
    <option value="s597dp392">s597dp392</option>
    <option value="s397dp095">s397dp095</option> 
    </select>

Run codeHide result

Answer 2

jQuery

function change() {
  if ($('#servergroup option:selected').length) {
    $('#servername').attr('disabled', false);
  }
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select id="servergroup" multiple="multiple" onchange='change()'>
    <option value="P1">P1</option>
    <option value="P2">P2</option>
    <option value="P3">P3</option>
    <option value="P4">P4</option>
</select>

<select id="servername" multiple="multiple" disabled>
    <option value="s597ap233">s597ap233</option>
    <option value="s597dp392">s597dp392</option>
    <option value="s397dp095">s397dp095</option> 
</select>

Run codeHide result

Answer 3

<option value="-1"> -Select Server Group- </option>

<option value="-1"> -Select Server Name- </option>

" " .

, JQuery as Follows:

$(document).ready(function ()
{
    //making serverName Dropdown box disabled by default.
    $('#servername').prop('disabled', true);

    $('#servergroup').change(function ()
    {
        if($(this).val == "-1")
        {
           $('#servername').val = "-1";
           $('#servername').prop('disabled', true);
        }
        else
        {   
          $('#servername').prop('disabled', false); 
        }  
    });
});