var trackNumber = 0;

function nextTrack() {
 trackNumber = trackNumber + 1;
 updateStuff();
}

function previousTrack() {
 trackNumber = trackNumber - 1;
 updateStuff();
}

function checkMusic() {
 
}

function updateStuff() {
 document.getElementById('trackNum').innerHTML = trackNumber;
}

@@ -45,32 +45,39 @@
 %0A trackNumber = 
+Number(
 trackNumber + 1;
@@ -75,16 +75,17 @@
 mber + 1
+)
 ;%0A updat
@@ -139,16 +139,23 @@
 umber = 
+Number(
 trackNum
@@ -161,16 +161,17 @@
 mber - 1
+)
 ;%0A updat

Update tRemix.js