Haha

ajax.js

{% block js_block %}

<script>

  $("#project-select").change(function (){
    var pro_gene = $(this).val();
      $.ajax({
        url: '{% url "gene_expdb" %}',
        data: {
          'pro_gene': pro_gene,
        },
        dataType: 'json',
        success: function (data) {
          if (data) {
            alert("A user with this username already exists.");
          }
        }
      });
  });
</script>
{% endblock %}