Add instanceof wrapper that avoids TypeError when second argument is undefined

1 files changed, 5 insertions, 2 deletions

diff --git a/src/js/plyr.js b/src/js/plyr.js
index 59e8c8ef..a563e345 100644
--- a/src/js/plyr.js
+++ b/src/js/plyr.js
@@ -373,10 +373,10 @@
                 return input !== null && input instanceof Event;
             },
             cue: function(input) {
-                return input !== null && (input instanceof window.TextTrackCue || input instanceof window.VTTCue);
+                this.instanceOf(input, window.TextTrackCue) || this.instanceOf(input, window.VTTCue);
             },
             track: function(input) {
-                return input !== null && (input instanceof window.TextTrack || typeof input.kind === 'string');
+                return input !== null && (this.instanceOf(input, window.TextTrack) || typeof input.kind === 'string');
             },
             undefined: function(input) {
                 return input !== null && typeof input === 'undefined';
@@ -389,6 +389,9 @@
                     (this.object(input) && Object.keys(input).length === 0)
                 );
             },
+            instanceOf: function(input, constructor) {
+                return Boolean(input && constructor && input instanceof constructor);
+            },
         },
 
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