how to change dropdowns values based on a selection of another dropdown using jquery

Question

I have my first dropdown with 2 selections: Standard Glass and Tempered glass. I have another dropdown where the user can select the width of the glass.

My problem:

Answer 1

I would suggest having just two selects, then changing the 2nd select based on what is selected in the first.

$('#typeOfGlass').on('change', function(){
    $('#glassWidth').html('');
    if($('#typeOfGlass').val()==15){
        $('#glassWidth').append('19');
        $('#glassWidth').append('20');
        $('#glassWidth').append('21');
    }else{
        $('#glassWidth').append('6');
        $('#glassWidth').append('7');
        $('#glassWidth').append('8');
        $('#glassWidth').append('9');
    }
});

Here is a working example: https://jsfiddle.net/6hmpa1ax/