update syntax and comments

src/controller/audio-stream-controller.js

@@ -348,7 +348,7 @@ class AudioStreamController extends EventHandler {
                 if (!isNaN(frag.sn)) {
                   this.nextLoadPosition = frag.start + frag.duration;
                 }
-                hls.trigger(Event.FRAG_LOADING, {frag: frag});
+                hls.trigger(Event.FRAG_LOADING, {frag});
                 this.state = State.FRAG_LOADING;
               }
             }
@@ -664,6 +664,7 @@ class AudioStreamController extends EventHandler {
       }
 
       if(!fragCurrent.mediaChannels) {
+        // Set is used because the elements do not repeat
         fragCurrent.mediaChannels = new Set();
       }
       fragCurrent.mediaChannels.add(data.type);

src/controller/buffer-controller.js

@@ -222,14 +222,9 @@ class BufferController extends EventHandler {
     // count nb of pending segments waiting for appending on this sourcebuffer
     let pending = this.segments.reduce( (counter, segment) => (segment.parent === parent) ? counter + 1 : counter , 0);
 
-
     // this.sourceBuffer is better to use than media.buffered as it is closer to the PTS data from the fragments
-    let timeRanges = new Map();
-    for (let type in this.sourceBuffer) {
-      if (this.sourceBuffer.hasOwnProperty(type)) {
-        timeRanges.set(type, this.sourceBuffer[type].buffered);
-      }
-    }
+    const bufferedEntries = Object.entries(this.sourceBuffer).map(([k,v]) => [k, v.buffered]);
+    const timeRanges = new Map(bufferedEntries);
 
     this.hls.trigger(Event.BUFFER_APPENDED, { parent, pending, timeRanges });
     // don't append in flushing mode

src/controller/stream-controller.js

@@ -1101,6 +1101,7 @@ class StreamController extends EventHandler {
       }
 
       if(!frag.mediaChannels) {
+        // Set is used because the elements do not repeat
         frag.mediaChannels = new Set();
       }
       frag.mediaChannels.add(data.type);