I have a HTML Multi select box

<form action=form_action.php method=Post>

<select name=cars[] multiple id=select_id>

    <option value=all id=option_id>All</option>

    <option value=volvo>Volvo</option>

    <option value=saab>Saab</option>

    <option value=opel>Opel</option>

    <option value=audi>Audi</option>

</select>

<input type=submit>

</form>

What I am trying to do is check if option All is selected or not in jQuery.

What I have tried is

<script>

        $(document).ready(function()

        {

            $('#option_id')

                .click(

                    function()

                    {

                        if ($(#select_id option[value='all']).length == 0) { //value does not exist so add

                            //Do something if not selected

                        }

                        else

                        {

                            //DO something if selected

                        }

                        //$(#select_id option:selected).removeAttr(selected);           //Remove

                        //$(#select_id option).attr('selected', 'selected');      //Add

                    }

                );

        });

    </script>

But it is not working.

Can anyone help me please?

Thanks in advance for helping.