javascript multiple conditions don't work

Question

I have a dropdown list ,every option of the list have a year and a month . I want to sort a select options according to year or month or both that are . so I can display options sorted by year or month or year and month together or show everything . I have the following event :

     $('#years,#months').bind('change', function () {
         y = $('#years').val();
         m = $('#months').val();
         $('#files > option').each(function () {
             $(this).show();
         });
         $('#files > option').each(function () {
             string = $(this).text();
              //first situation 
             if (y == 'All' && m == 'All')
                $(this).show();
            // second situation 
             else if ((y == 'All') && string.indexOf(m) == -1) 
                    $(this).hide();
            //third situation 
             else if ( string.indexOf(y) == -1 && m == 'All') 
                  $(this).hide();
             // fourth situation 
             else if (string.indexOf(y) == -1 || string.indexOf(m) == -1) 
               $(this).hide();
         });
     });

with html code :

<select id='years'>
    <option value='All'>All</option>
    <option value='2013'>2013</option>
    <option value='2012'>2012</option>
</select>
<select id='months'>
    <option value='All'>All</option>
    <option value='Feb'>Feb</option>
    <option value='Jan'>Jan</option>
</select>
<br/>
<br/>
<select id='files' siz='10'>
    <option value='0'>sdgsdfsadfsd1-2013-Feb-1212</option>
    <option value='1'>fsadfadsfadsfadsf2-2012-Feb-123123</option>
    <option value='2'>fsadfadsfadsfadsf3-2012-Jan-123123</option>
    <option value='3'>fsadfadsfadsfadsf4-2013-Jan-123123</option>
    <option value='4'>fsadfadsfadsfadsf5-2012-Feb-123123</option>
    <option value='5'>fsadfadsfadsfadsf6-2013-Feb-123123</option>
    <option value='6'>fsadfadsfadsfadsf7-2013-Feb-123123</option>
    <option value='7'>fsadfadsfadsfadsf8-2013-Jan-123123</option>
    <option value='8'>fsadfadsfadsfadsf9-2012-Jan-123123</option>
    <option value='9'>fsadfadsfadsfadsf10-2013-Feb-123123</option>
    <option value='10'>fsadfadsfadsfadsf11-2012-Feb-123123</option>
</select>

second and third situations are not working !! it deals with the two conditions (true && false) , (false && true ) as they are same values ! I have no idea why ! here's a Demo

Answer 1

Your logic is wrong; the last condition is being evaluated when it shouldn't be. (For instance: if y == 'All' and also string.indexOf(m) >= 0). Try this instead:

$('#files > option').each(function () {
    var string = $(this).text();
    var show;
    if (y == 'All') {
        show = m == 'All' || string.indexOf(m) >= 0;
    } else if (m == 'All') {
        show = string.indexOf(y) >= 0;
    } else {
        show = string.indexOf(y) >= 0 && string.indexOf(m) >= 0;
    }
    if (show) $(this).show();
    else $(this).hide();
});