Update '12/player.js'

12/player.js

@@ -6,6 +6,10 @@ track.addEventListener('cuechange', function () {
   var d = JSON.parse(cues[0].text);
   console.log("d",d);
   track_div.innerHTML = d.title;
+  var old = document.querySelector(".now_playing");
+  	if (old) {
+      old.classList.remove("now_playing");
+    }
   var playing = document.getElementById(d.title);
   playing.classList.add("now_playing");
   console.log("playing",playing);