Set focus to a button inside bootstrap modal when it opens

Question

I am trying to achieve the following:

1. When the page loads, the focus goes to the first element in the form.
2. When the button is pressed on form, a modal appears to confirm and the focus should be on the "Proceed" button inside modal dialog.

I managed to to make the first one work, but for the second I have no idea why it is not working. Following is my code.

HTML

<form method="post" {% if action %} action="{{ action }}" {% endif %} role="form" enctype="multipart/form-data">
<!-- Modal -->
  <div class="modal fade" id="confirmationModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
    <div class="modal-dialog" role="document">
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal" aria-label="Close">
            <span aria-hidden="true">&times;</span>
          </button>
          <h4 class="modal-title" id="myModalLabel">Confirmation</h4>
        </div>
        <div class="modal-body">
           {{ confirm | default: "Would you like to proceed?" }}
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
          <button type="submit" id="submit-main-form" class="btn btn-primary">
              <i class="fa fa-save"></i> {{ submit_text | default: "Proceed" }}
          </button>
        </div>
      </div>
    </div>
  </div>

</form>

Script

/* Sets focus on the first element of the form */
$(document).ready(function() {

    $('form:first *:input[type!=hidden]:first').focus();

    $("#confirmationModal").on('show.bs.modal', function(event) {
        // not setting focus to submit button
        $("#submit-main-form").focus();
    });
});

Solution

You are using show.bs.modal which Occurs when the modal is about to be shown

I believe you need shown.bs.modal event which Occurs when the modal is fully shown along when all the CSS transitions are completed.

See Bootstrap modal reference.