Second drop-down options based on first drop-down

Answer 1

You could try like this.

First hide all the options and show only matching options using toggleClass()

$(function() {

    $('#independent').on('change', function (e) {
    $('#dependent').val('');
        var endingChar = $(this).val().split('').pop();       
        var selected = $( '#independent' ).val();
          $('#dependent option').addClass('show');
 
          $('#dependent option[value^='+selected+']').toggleClass('show');
    })

});

.show{
display:none;
}