Add comment, refactor, handle edge cases

common/lib/xmodule/xmodule/js/src/video/00_sjson.js

@@ -62,15 +62,24 @@ function() {
         };
 
         function filter(start, end) {
+            /* filters captions that occur between inputs
+             * `start` and `end`. Start and end should
+             * be Numbers (doubles) corresponding to the
+             * number of seconds elapsed since the beginning
+             * of the video.
+             *
+             * Returns an object with properties
+             * "start" and "captions" representing
+             * parallel arrays of start times and
+             * their corresponding captions.
+             */
             var filteredTimes = [];
             var filteredCaptions = [];
             var startTimes = getStartTimes();
             var captions = getCaptions();
-            var currentStartTime;
-            var i;
 
             if (startTimes.length !== captions.length) {
-                return [];
+                throw new Exception("video caption and start time arrays do not match in length");
             }
 
             // if end is null, then it's been set to
@@ -80,17 +89,16 @@ function() {
                 end = startTimes[startTimes.length - 1];
             }
 
-            for (i = 0; i < startTimes.length; i++) {
-              currentStartTime = startTimes[i];
-              if (currentStartTime >= start && currentStartTime <= end) {
-                filteredTimes.push(currentStartTime);
-                filteredCaptions.push(captions[i]);
-              }
-            }
+            _.filter(startTimes, function(currentStartTime, i) {
+                if (currentStartTime >= start && currentStartTime <= end) {
+                    filteredTimes.push(currentStartTime);
+                    filteredCaptions.push(captions[i]);
+                }
+            });
 
             return {
-              'start': filteredTimes,
-              'captions': filteredCaptions
+                'start': filteredTimes,
+                'captions': filteredCaptions
             };
         }
 

common/lib/xmodule/xmodule/js/src/video/03_video_player.js

@@ -818,7 +818,7 @@ function (HTML5Video, Resizer) {
             endTime = this.videoPlayer.duration(),
             youTubeId;
 
-        if (this.config.endTime !== null) {
+        if (this.config.endTime) {
             endTime = Math.min(this.config.endTime, endTime);
         }
 

common/lib/xmodule/xmodule/js/src/video/06_video_progress_slider.js

@@ -166,7 +166,7 @@ function () {
         var time = ui.value,
             endTime = this.videoPlayer.duration();
 
-        if (this.config.endTime !== null) {
+        if (this.config.endTime) {
             endTime = Math.min(this.config.endTime, endTime);
         }