@@ -182,6 +182,39 @@
     </li>
   </ul>
 <script>
+
+//querySelectorAll to retrieve a nodeList of <li data-time>
+//Use Array.from to convert nodelist into array
+const timeNodes = Array.from(document.querySelectorAll('[data-time]'));  
+
+//To get the total # of seconds for all videos
+//1. Use .map() to get each node.dataset.time
+//2. use .map() again to convert each node.dataset.time from M:S format to seconds
+//3. Finally use .reduce() to sum up total # of seconds for all videos.
+const seconds = timeNodes.map((node) => {
+	return node.dataset.time;
+}).map((timeCode) => {
+		timeCodeArray = timeCode.split(':').map(parseFloat);  //From 6:10 to [6,10] //Need to use .map(parseFloat) to convert string to float so we can perform math operations
+		totalSec = (timeCodeArray[0] * 60) + timeCodeArray[1]; 
+		return totalSec;
+}).reduce((total,sec) => {    //Use reduce to get the total of seconds
+	total = total + sec;
+	return total;
+});
+console.log("Total seconds: " + seconds);  //Now we got the total seconds
+
+//Convert total seconds into Hours:Minutes:seconds format
+let secondsLeft = seconds;
+//Get total hours
+const hours = Math.floor(secondsLeft / 3600);  
+secondsLeft = secondsLeft % 3600;
+
+//Get total mins
+const mins = Math.floor(secondsLeft / 60);
+secondsLeft = secondsLeft % 60;
+
+
+console.log(`${hours}:${mins}:${secondsLeft}`);
 </script>
 </body>
 </html>