make sure that timer callback hasn't already been removed by another …

…listener during emit(), see #248
phetsims · May 17, 2019 · 9229be6 · 9229be6
1 parent d845ea4
commit 9229be6
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/js/timer.js b/js/timer.js
@@ -36,8 +36,12 @@ define( require => {
 
         // Convert seconds to ms and see if item has timed out
         if ( elapsed * 1000 >= timeout ) {
-          listener();
-          this.removeListener( callback );
+
+          // make sure that this callback hasn't already been removed by another listener while emit() is in progress
+          if ( this.hasListener( callback ) ) {
+            listener();
+            this.removeListener( callback );
+          }
         }
       };
       this.addListener( callback );