JAVASCRIPT

js select on change value

document.getElementById('my-select').addEventListener('change', function() {
  console.log('You selected: ', this.value);
});

javascript select change selected

const options = Array.from(select.options);
options.forEach((option, i) => {
  if (option.value === use_id) select.selectedIndex = i;
});

change on select with javascript

$("#select1").change(function() {
  if ($(this).data('options') === undefined) {
    /*Taking an array of all options-2 and kind of embedding it on the select1*/
    $(this).data('options', $('#select2 option').clone());
  }
  var id = $(this).val();
  var options = $(this).data('options').filter('[value=' + id + ']');
  $('#select2').html(options);
});