Error writing IF and Else in jquery [duplicate]

I'm starting to venture into the development world now and hit a question when using IF and Else.

The code below is OK

    <select id="course_list" >
      <?php $my_query = new WP_Query('tribe_events_cat=petroleo-e-gas'); ?>
         <?php while ($my_query->have_posts()) : $my_query->the_post(); ?>
            <option value="course_<?php the_ID(); ?>" >
                <?php the_title(); ?>
            </option>
        <?php endwhile; ?>
    </select>

<script type="text/javascript">
$("#course_list").on('change', function(){
        $('.course_item').hide();
        $('#' + this.value).show();

    });
</script>

But when I try to refine the code and show all courses again, everything has stopped working.

<select id="course_list" >
        <?php $my_query = new WP_Query('tribe_events_cat=petroleo-e-gas'); ?>
        <?php while ($my_query->have_posts()) : $my_query->the_post(); ?>
        <option value="all-posts" >
            Mostrar Todos
        </option>
        <option value="course_<?php the_ID(); ?>" >
            <?php the_title(); ?>
        </option>
        <?php endwhile; ?>
    </select>
    <script type="text/javascript">
    $("#course_list").on('change', function(){

        if {
            $('.course_item').hide();
            $('#' + this.value).show();
           }

        else

            $('.course_item=').show();


        });
    </script>