Optimized presence timer implementation

public/js/mc.js

@@ -361,24 +361,29 @@ function initQuillEdit(_selector = '.note-content[auto-edit]') {
     // });
 }
 
+var patientPresenceTimer = false;
 function initPatientPresenceIndicator() {
-    var presenceTimer = false;
-    if(presenceTimer !== false) {
-        window.clearInterval(presenceTimer);
-        presenceTimer = false;
+    if(patientPresenceTimer !== false) {
+        window.clearInterval(patientPresenceTimer);
+        patientPresenceTimer = false;
+        console.log('Cancelled previous timer!');
     }
     var elem = $('.patient-presence-indicator[data-patient-uid]');
     if(elem.length) {
         var patientUid = elem.attr('data-patient-uid');
-        presenceTimer = window.setInterval(function() {
-            $.get('/patients/' + patientUid + '/presence', function(_data) {
-                if(_data.online) {
-                    elem.addClass('online');
-                }
-                else {
-                    elem.removeClass('online');
-                }
-            }, 'json');
+        patientPresenceTimer = window.setInterval(function() {
+            var elem = $('.patient-presence-indicator[data-patient-uid]');
+            if(elem.length) {
+                var patientUid = elem.attr('data-patient-uid');
+                $.get('/patients/' + patientUid + '/presence', function(_data) {
+                    if(_data.online) {
+                        elem.addClass('online');
+                    }
+                    else {
+                        elem.removeClass('online');
+                    }
+                }, 'json');
+            }
         }, 2500);
     }
 }