JSFiddle - React, Tailwind, and code Playground

HTML

Jenjang: <select id='x'></select><br/>
Jurusan: <select id='y'></select>

JavaScript

var data = {
    'S1': ['TI'],
    'D3': ['TI', 'MI']
};

var select = $('#x');
for(var i in data)
{
    var dt = data[i];
    select.append(
        $('<option>').val( i ).text( i ).data('jurusan', dt)
    ) 
}

select.change(function(){
    var j = $('#y');
    $('option', j).remove();
    var dt = $('option:selected', this).data('jurusan');
    for(var i in dt)
    {
         $(j).append( $('<option>').val( dt[i] ).text( dt[i] ) )
    }
}).trigger('change');