Disable big button when entries are disabled

app/templates/main.html

@@ -3,7 +3,7 @@
 {% extends 'base.html' %}
 {% block title %}Warteliste{% endblock %}
 {% block content %}
-<a role="button" class="btn btn-primary btn-lg btn-block mb-2" href="/list">Eintragen</a>
+<button id="bfb" role="button" class="btn btn-primary btn-lg btn-block mb-2" href="/list">Eintragen</button>
 <table class="table"
         data-toggle="table"
         data-url="/api/queue"
@@ -18,4 +18,15 @@
     </thead>
 </table>
 <a name="end"></a>
+{% endblock %}
+{% block extrajs %}
+<script>
+$.getJSON("/api/entries/accept", (data) => {
+    if (data["value"]==0) {
+        $("#bfb").addClass("disabled")
+        $("#bfb").prop("aria-disabled",true);
+        $("#bfb").prop("tabindex","-1");
+    }
+})
+</script>
 {% endblock %}