Filter Selectbox Options Depending On Primary Choice

I am creating some selectboxes where i need to restrict my options depending on the choice made in the primary. Basically i have Select field 1 and Select field 2. Data for these s

Solution 1:

See this question. Basically, you need to add a change event and check $(this).val(). From there you simply create option-elements and add them as the html to your select box 2.

$('#select1').change(function() {
    var options = '';
    if($(this).val() == 'a') {
        options = '<option value="1">1</option><option value="2">2</option>';
    }
    else if ($(this).val() == 'b'){
        options = '<option value="3">3</option><option value="4">4</option>';
    }

    $('#select2').html(options);
});

EDIT: I didn't understand if you wanted to actually filter the values, remove values, or add however many you wish. If you really want to filter out elements you can use my change event and combine that with .filter().