call ajax on SELECT change (in rails view)

my_view.html.erb

<script type="text/javascript">
$(document).on("change", "#my_select", callAjax);

$.ajaxSetup({
  headers: { 'X-CSRF-Token': '<%= form_authenticity_token.to_s %>' },
  timeout: 30000, // timeout after 30 seconds
  async: true,
});

function callAjax() {

  $('#content').text('loading classes, please wait...');

  $.ajax({
    type: 'GET',
    url: '<%= ajax_path(format: :json).html_safe %>',
    dataType: "json",
    data: { id: $('#my_select').val() },
  }).done( function (data, status) {
    // console.log(data);
    $('#content').html('');
    for (var i = 0; i < data.length; i++) {
      var ec = data[i];
      var $label = $('<label class="control-label" for="class_number_' + ec['id'] + '">' + ec['name'] + '</label>');
      var $input = $('<div class="controls"><input id="class_number_' + ec['id'] + '" name="class_numbers[' + ec['id'] + ']" type="text" /></div>');
      var $row = $('<div class="control-group">').append($label).append($input);
      $('#content').append($row);
    }
  }).fail( function (data, status) {
    $('#content').text("update server error: " + data.status + ' ' + data.statusText + '\n' + data.responseText);
  });
}
</script>