Audio Player: let/const and arrow function

Convert `var` to let/const as pointed by presumit.

Convert an anonymous function to arrow function to avoid the `.bind(this)`.

No change in behavior.

Test: Manually tested the audio player (just in case).
Change-Id: I73be16d039476b9fe9a087798f596a521b1bdabc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2525884
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Jeremie Boulic <jboulic@chromium.org>
Commit-Queue: Jeremie Boulic <jboulic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825293}

ui/file_manager/audio_player/elements/audio_player.js

@@ -121,7 +121,7 @@ Polymer({
     this.$.audio.addEventListener('ended', this.onAudioEnded.bind(this));
     this.$.audio.addEventListener('error', this.onAudioError.bind(this));
 
-    var onAudioStatusUpdatedBound = this.onAudioStatusUpdate_.bind(this);
+    const onAudioStatusUpdatedBound = this.onAudioStatusUpdate_.bind(this);
     this.$.audio.addEventListener('timeupdate', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('ended', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('play', onAudioStatusUpdatedBound);
@@ -147,10 +147,10 @@ Polymer({
    * @param {number} oldValue old value.
    */
   currentTrackIndexChanged: function(newValue, oldValue) {
-    var currentTrackUrl = '';
+    let currentTrackUrl = '';
 
     if (oldValue != newValue) {
-      var currentTrack = this.$.trackList.getCurrentTrack();
+      const currentTrack = this.$.trackList.getCurrentTrack();
       if(currentTrack && currentTrack != this.$.trackInfo.track){
         this.$.trackInfo.track = currentTrack;
         this.$.trackInfo.artworkAvailable = !!currentTrack.artworkUrl;
@@ -176,7 +176,7 @@ Polymer({
   playingChanged: function(newValue, oldValue) {
     if (newValue) {
       if (!this.$.audio.src) {
-        var currentTrack = this.$.trackList.getCurrentTrack();
+        const currentTrack = this.$.trackList.getCurrentTrack();
         if (currentTrack && currentTrack.url != this.$.audio.src) {
           this.$.audio.src = currentTrack.url;
         }
@@ -284,13 +284,14 @@ Polymer({
   advance_: function(forward, repeat) {
     this.cancelAutoAdvance_();
 
-    var nextTrackIndex = this.$.trackList.getNextTrackIndex(forward, true);
-    var isNextTrackAvailable =
+    const nextTrackIndex = this.$.trackList.getNextTrackIndex(forward, true);
+    const isNextTrackAvailable =
         (this.$.trackList.getNextTrackIndex(forward, repeat) !== -1);
 
     this.playing = isNextTrackAvailable;
 
-    var shouldFireEvent = this.$.trackList.currentTrackIndex === nextTrackIndex;
+    const shouldFireEvent =
+        this.$.trackList.currentTrackIndex === nextTrackIndex;
     this.$.trackList.currentTrackIndex = nextTrackIndex;
     this.$.audio.currentTime = 0;
     this.time = 0;
@@ -319,29 +320,27 @@ Polymer({
    */
   scheduleAutoAdvance_: function(forward, repeat) {
     this.cancelAutoAdvance_();
-    var currentTrackIndex = this.currentTrackIndex;
-
-    var timerId = setTimeout(
-        function() {
-          // If the other timer is scheduled, do nothing.
-          if (this.autoAdvanceTimer_ !== timerId) {
-            return;
-          }
-
-          this.autoAdvanceTimer_ = null;
-
-          // If the track has been changed since the advance was scheduled, do
-          // nothing.
-          if (this.currentTrackIndex !== currentTrackIndex) {
-            return;
-          }
-
-          // We are advancing only if the next track is not known to be invalid.
-          // This prevents an endless auto-advancing in the case when all tracks
-          // are invalid (we will only visit each track once).
-          this.advance_(forward, repeat);
-        }.bind(this),
-        3000);
+    const currentTrackIndex = this.currentTrackIndex;
+
+    const timerId = setTimeout(() => {
+      // If the other timer is scheduled, do nothing.
+      if (this.autoAdvanceTimer_ !== timerId) {
+        return;
+      }
+
+      this.autoAdvanceTimer_ = null;
+
+      // If the track has been changed since the advance was scheduled, do
+      // nothing.
+      if (this.currentTrackIndex !== currentTrackIndex) {
+        return;
+      }
+
+      // We are advancing only if the next track is not known to be invalid.
+      // This prevents an endless auto-advancing in the case when all tracks
+      // are invalid (we will only visit each track once).
+      this.advance_(forward, repeat);
+    }, 3000);
 
     this.autoAdvanceTimer_ = timerId;
   },
@@ -376,7 +375,7 @@ Polymer({
     this.cancelAutoAdvance_();
 
     this.$.trackList.tracks = tracks;
-    var currentTrack = this.$.trackList.getCurrentTrack();
+    const currentTrack = this.$.trackList.getCurrentTrack();
     if (currentTrack && currentTrack.url != this.$.audio.src) {
       this.$.audio.src = currentTrack.url;
       this.$.audio.play();
@@ -402,7 +401,7 @@ Polymer({
         this.$.trackInfo.track.url === this.tracks[index].url){
       this.$.trackInfo.notifyPath('track.title', this.tracks[index].title);
       this.$.trackInfo.notifyPath('track.artist', this.tracks[index].artist);
-      var artworkUrl = this.tracks[index].artworkUrl;
+      const artworkUrl = this.tracks[index].artworkUrl;
       if (artworkUrl) {
         this.$.trackInfo.notifyPath('track.artworkUrl',
             this.tracks[index].artworkUrl);

ui/file_manager/audio_player/elements/track_list.js

@@ -11,7 +11,7 @@
  *   active: boolean
  * }}
  */
-var TrackInfo;
+let TrackInfo;
 
 (function() {
   'use strict';
@@ -99,7 +99,7 @@ var TrackInfo;
       }
 
       if (0 <= newValue && newValue < this.tracks.length) {
-        var currentPlayOrder = this.playOrder.indexOf(newValue);
+        const currentPlayOrder = this.playOrder.indexOf(newValue);
         if (currentPlayOrder !== -1) {
           // Success
           this.set('tracks.' + newValue + '.active', true);
@@ -146,8 +146,8 @@ var TrackInfo;
      * @param {Event} event Click event.
      */
     trackClicked: function(event) {
-      var index = ~~event.currentTarget.getAttribute('index');
-      var track = this.tracks[index];
+      const index = ~~event.currentTarget.getAttribute('index');
+      const track = this.tracks[index];
       if (track) {
         this.selectTrack(track);
       }
@@ -159,12 +159,12 @@ var TrackInfo;
      * @private
      */
     ensureTrackInViewport_: function(trackIndex) {
-      var trackElement = this.$$('.track[index="' + trackIndex + '"]');
+      const trackElement = this.$$('.track[index="' + trackIndex + '"]');
       if (trackElement) {
-        var viewTop = this.scrollTop;
-        var viewHeight = this.clientHeight;
-        var elementTop = trackElement.offsetTop - this.offsetTop;
-        var elementHeight = trackElement.offsetHeight;
+        const viewTop = this.scrollTop;
+        const viewHeight = this.clientHeight;
+        const elementTop = trackElement.offsetTop - this.offsetTop;
+        const elementHeight = trackElement.offsetHeight;
 
         if (elementTop <= viewTop) {
           // Adjust the tops.
@@ -231,8 +231,8 @@ var TrackInfo;
      *     track.
      */
     selectTrack: function(track) {
-      var index = -1;
-      for (var i = 0; i < this.tracks.length; i++) {
+      let index = -1;
+      for (let i = 0; i < this.tracks.length; i++) {
         if (this.tracks[i].url === track.url) {
           index = i;
           break;
@@ -276,21 +276,21 @@ var TrackInfo;
         return -1;
       }
 
-      var defaultTrackIndex =
+      const defaultTrackIndex =
           forward ? this.playOrder[0] : this.playOrder[this.tracks.length - 1];
 
-      var currentPlayOrder = this.playOrder.indexOf(this.currentTrackIndex);
+      const currentPlayOrder = this.playOrder.indexOf(this.currentTrackIndex);
       console.assert(
           (0 <= currentPlayOrder && currentPlayOrder < this.tracks.length),
           'Insufficient TrackList.playOrder. The current track is not on the ' +
               'track list.');
 
-      var newPlayOrder = currentPlayOrder + (forward ? +1 : -1);
+      const newPlayOrder = currentPlayOrder + (forward ? +1 : -1);
       if (newPlayOrder === -1 || newPlayOrder === this.tracks.length) {
         return cyclic ? defaultTrackIndex : -1;
       }
 
-      var newTrackIndex = this.playOrder[newPlayOrder];
+      const newTrackIndex = this.playOrder[newPlayOrder];
       console.assert(
           (0 <= newTrackIndex && newTrackIndex < this.tracks.length),
           'Insufficient TrackList.playOrder. New Play Order: ' + newPlayOrder);