Prefer const over let.

A coming update to the Google eslint config will require using "const"
over "let".  This makes that one change to isolate the big changes.

Change-Id: I7d0974c3ae15c53cc45a6b07bf9f6586e2d34aca

.eslintrc.js

@@ -63,6 +63,7 @@ module.exports = {
         "brace-style": ["error", "1tbs", { "allowSingleLine": true }],
         "key-spacing": ["error", {"beforeColon": false, "afterColon": true}],
         "no-multi-spaces": ["error", { "ignoreEOLComments": true }],
+        "prefer-const": ["error", {"ignoreReadBeforeAssign": true}],
         // }}}
 
         // "Possible error" rules in "eslint:recommended" that need options: {{{

demo/asset_card.js

@@ -128,7 +128,7 @@ class AssetCard {
       }
     }
 
-    for (let drm of asset.drm) {
+    for (const drm of asset.drm) {
       switch (drm) {
         case KeySystem.WIDEVINE:
           this.addFeatureIcon_('widevine', 'Widevine DRM');

demo/cast_receiver/receiver_app.js

@@ -63,13 +63,13 @@ ShakaReceiver.prototype.init = function() {
   shaka.polyfill.installAll();
 
   /** @type {HTMLMediaElement} */
-  let video = /** @type {HTMLMediaElement} */
+  const video = /** @type {HTMLMediaElement} */
       (document.getElementById('video'));
   goog.asserts.assert(video, 'Video element should be available!');
   this.video_ = video;
 
   /** @type {!shaka.ui.Overlay} */
-  let ui = this.video_['ui'];
+  const ui = this.video_['ui'];
   goog.asserts.assert(ui, 'UI should be available!');
 
   // Make sure we don't show extra UI elements we don't need on the TV.

demo/common/asset.js

@@ -251,14 +251,14 @@ const ShakaDemoAssetInfo = class {
     // Construct a generic object with the values of this object, but with the
     // proper formatting.
     const raw = {};
-    for (let key in this) {
+    for (const key in this) {
       const value = this[key];
       if (value instanceof Map) {
         // The built-in JSON functions cannot convert Maps; this converts Maps
         // to objects.
         const replacement = {};
         replacement['__type__'] = 'map';
-        for (let entry of value.entries()) {
+        for (const entry of value.entries()) {
           replacement[entry[0]] = entry[1];
         }
         raw[key] = replacement;
@@ -317,7 +317,7 @@ const ShakaDemoAssetInfo = class {
       });
     }
     if (this.extraConfig) {
-      for (let key in this.extraConfig) {
+      for (const key in this.extraConfig) {
         config[key] = this.extraConfig[key];
       }
     }
@@ -361,11 +361,11 @@ const ShakaDemoAssetInfo = class {
   static fromJSON(raw) {
     // This handles the special case for Maps in toJSON.
     const parsed = {};
-    for (let key in raw) {
+    for (const key in raw) {
       const value = raw[key];
       if (value && typeof value == 'object' && value['__type__'] == 'map') {
         const replacement = new Map();
-        for (let key in value) {
+        for (const key in value) {
           if (key != '__type__') {
             replacement.set(key, value[key]);
           }

demo/config.js

@@ -139,7 +139,7 @@ class ShakaDemoConfig {
       // All robustness fields of a given type are set at once.
       this.addDatalistInput_(name, robustnessSuggestions, (input) => {
         // Add in any common drmSystem not currently in advanced.
-        for (let drmSystem of commonDrmSystems) {
+        for (const drmSystem of commonDrmSystems) {
           if (!(drmSystem in advanced)) {
             advanced[commonDrmSystems] = {
               distinctiveIdentifierRequired: false,
@@ -152,7 +152,7 @@ class ShakaDemoConfig {
           }
         }
         // Set the robustness.
-        for (let drmSystem in advanced) {
+        for (const drmSystem in advanced) {
           advanced[drmSystem][valueName] = input.value;
         }
         shakaDemoMain.configure('drm.advanced', advanced);

demo/demo_utils.js

@@ -17,7 +17,7 @@
 
 
 /** @namespace */
-let ShakaDemoUtils = {};
+const ShakaDemoUtils = {};
 
 /**
  * Goes through the various values in shaka.extern.PlayerConfiguration, and
@@ -37,8 +37,8 @@ ShakaDemoUtils.runThroughHashParams = (callback, config) => {
   // This exists for legacy reasons; the previous demo page had some hash values
   // set to names that did not match the names of their corresponding config
   // object name.
-  let overridden = [];
-  let configOverride = (hashName, configName) => {
+  const overridden = [];
+  const configOverride = (hashName, configName) => {
     overridden.push(configName);
     callback(hashName, configName);
   };
@@ -58,16 +58,16 @@ ShakaDemoUtils.runThroughHashParams = (callback, config) => {
   // This is to remove ambiguity in situations where there are two objects in
   // the config that share a key with the same name, without wasting space by
   // pointlessly adding namespace information to every value.
-  let added = [];
-  let collisions = [];
-  let findCollisions = (object) => {
-    for (let key in object) {
+  const added = [];
+  const collisions = [];
+  const findCollisions = (object) => {
+    for (const key in object) {
       if (added.includes(key) && !collisions.includes(key)) {
         collisions.push(key);
       }
       added.push(key);
 
-      let value = object[key];
+      const value = object[key];
       if (typeof value != 'number' && typeof value != 'string' &&
           typeof value != 'boolean') {
         findCollisions(value);
@@ -82,16 +82,16 @@ ShakaDemoUtils.runThroughHashParams = (callback, config) => {
   // discard any 'bufferBehind=' values from old hashes.
 
   // Now automatically do other config values.
-  let handleConfig = (object, accumulated) => {
-    for (let key in object) {
+  const handleConfig = (object, accumulated) => {
+    for (const key in object) {
       let hashName = key;
-      let configName = accumulated + key;
+      const configName = accumulated + key;
       if (overridden.includes(configName)) continue;
       if (collisions.includes(key)) {
         hashName = configName;
       }
 
-      let value = object[key];
+      const value = object[key];
       if (typeof value == 'number' || typeof value == 'string' ||
           typeof value == 'boolean') {
         callback(hashName, configName);

demo/input.js

@@ -114,7 +114,7 @@ class ShakaDemoSelectInput extends ShakaDemoInput {
     this.input_.classList.add('mdl-textfield__input');
     this.extra_.classList.add('mdl-textfield__label');
     this.extra_.setAttribute('for', this.input_.id);
-    for (let value of Object.keys(values)) {
+    for (const value of Object.keys(values)) {
       const option = document.createElement('option');
       option.textContent = values[value];
       option.value = value;

demo/main.js

@@ -198,7 +198,7 @@ class ShakaDemoMain {
     const localization = this.controls_.getLocalization();
     const UNKNOWN_LOCALES = shaka.ui.Localization.UNKNOWN_LOCALES;
     localization.addEventListener(UNKNOWN_LOCALES, (event) => {
-      for (let locale of event['locales']) {
+      for (const locale of event['locales']) {
         this.loadUILocale_(locale);
       }
     });
@@ -458,7 +458,7 @@ class ShakaDemoMain {
     }
 
     // Does the asset contain a playable mime type?
-    let mimeTypes = [];
+    const mimeTypes = [];
     if (asset.features.includes(shakaAssets.Feature.WEBM)) {
       mimeTypes.push('video/webm');
     }
@@ -516,7 +516,7 @@ class ShakaDemoMain {
 
     const obj = await response.json();
     const map = new Map();
-    for (let key in obj) {
+    for (const key in obj) {
       map.set(key, obj[key]);
     }
 
@@ -873,7 +873,7 @@ class ShakaDemoMain {
     params.push('uilang=' + this.getUILocale());
 
     const navButtons = document.getElementById('nav-button-container');
-    for (let button of navButtons.childNodes) {
+    for (const button of navButtons.childNodes) {
       if (button.nodeType == Node.ELEMENT_NODE &&
           button.classList.contains('mdl-button--accent')) {
         params.push('panel=' + button.textContent);
@@ -980,12 +980,12 @@ class ShakaDemoMain {
     // Add a click listener to display this container, and hide the others.
     const switchPage = () => {
       // This element should be the selected one.
-      for (let child of navButtons.childNodes) {
+      for (const child of navButtons.childNodes) {
         if (child.nodeType == Node.ELEMENT_NODE) {
           child.classList.remove('mdl-button--accent');
         }
       }
-      for (let child of contents.childNodes) {
+      for (const child of contents.childNodes) {
         if (child.nodeType == Node.ELEMENT_NODE) {
           this.hideNode_(child);
         }
@@ -1023,7 +1023,7 @@ class ShakaDemoMain {
   setUpVersionString_() {
     const version = shaka.Player.version;
     let split = version.split('-');
-    let inParen = [];
+    const inParen = [];
 
     // Separate out some special terms into parentheses after the rest of the
     // version, to make them stand out visually.
@@ -1125,7 +1125,7 @@ class ShakaDemoMain {
 }
 
 
-let shakaDemoMain = new ShakaDemoMain();
+const shakaDemoMain = new ShakaDemoMain();
 
 
 /**

demo/search.js

@@ -128,7 +128,7 @@ class ShakaDemoSearch {
         break;
       case ShakaDemoSearch.TermType.FEATURE:
         // Only this term should be in the desired features.
-        for (let term of others) {
+        for (const term of others) {
           const index = this.desiredFeatures_.indexOf(
               /** @type {shakaAssets.Feature} */ (term));
           if (index != -1) {
@@ -208,7 +208,7 @@ class ShakaDemoSearch {
     searchContainer.addRow(null, null);
     const nullOption = 'Unspecified';
     const valuesObject = {};
-    for (let term of choices) {
+    for (const term of choices) {
       if (type == 'DRM') {
         // The internal names of the keysystems aren't very readable, so use a
         // common name instead.
@@ -304,7 +304,7 @@ class ShakaDemoSearch {
       if (this.desiredSource_ && asset.source != this.desiredSource_) {
         return false;
       }
-      for (let feature of this.desiredFeatures_) {
+      for (const feature of this.desiredFeatures_) {
         if (feature == shakaAssets.Feature.STORED) {
           if (!asset.isStored()) {
             return false;

lib/abr/ewma.js

@@ -53,8 +53,8 @@ shaka.abr.Ewma = function(halfLife) {
  * @param {number} value
  */
 shaka.abr.Ewma.prototype.sample = function(weight, value) {
-  let adjAlpha = Math.pow(this.alpha_, weight);
-  let newEstimate = value * (1 - adjAlpha) + adjAlpha * this.estimate_;
+  const adjAlpha = Math.pow(this.alpha_, weight);
+  const newEstimate = value * (1 - adjAlpha) + adjAlpha * this.estimate_;
 
   if (!isNaN(newEstimate)) {
     this.estimate_ = newEstimate;
@@ -67,6 +67,6 @@ shaka.abr.Ewma.prototype.sample = function(weight, value) {
  * @return {number}
  */
 shaka.abr.Ewma.prototype.getEstimate = function() {
-  let zeroFactor = 1 - Math.pow(this.alpha_, this.totalWeight_);
+  const zeroFactor = 1 - Math.pow(this.alpha_, this.totalWeight_);
   return this.estimate_ / zeroFactor;
 };

lib/abr/ewma_bandwidth_estimator.js

@@ -89,8 +89,8 @@ shaka.abr.EwmaBandwidthEstimator.prototype.sample = function(
     return;
   }
 
-  let bandwidth = 8000 * numBytes / durationMs;
-  let weight = durationMs / 1000;
+  const bandwidth = 8000 * numBytes / durationMs;
+  const weight = durationMs / 1000;
 
   this.bytesSampled_ += numBytes;
   this.fast_.sample(weight, bandwidth);

lib/abr/simple_abr_manager.js

@@ -112,7 +112,7 @@ shaka.abr.SimpleAbrManager.prototype.chooseVariant = function() {
   // Get sorted Variants.
   let sortedVariants = SimpleAbrManager.filterAndSortVariants_(
       this.config_.restrictions, this.variants_);
-  let currentBandwidth = this.bandwidthEstimator_.getBandwidthEstimate(
+  const currentBandwidth = this.bandwidthEstimator_.getBandwidthEstimate(
       this.config_.defaultBandwidthEstimate);
 
   if (this.variants_.length && !sortedVariants.length) {
@@ -131,12 +131,12 @@ shaka.abr.SimpleAbrManager.prototype.chooseVariant = function() {
   let chosen = sortedVariants[0] || null;
 
   for (let i = 0; i < sortedVariants.length; ++i) {
-    let variant = sortedVariants[i];
-    let nextVariant = sortedVariants[i + 1] || {bandwidth: Infinity};
+    const variant = sortedVariants[i];
+    const nextVariant = sortedVariants[i + 1] || {bandwidth: Infinity};
 
-    let minBandwidth = variant.bandwidth /
+    const minBandwidth = variant.bandwidth /
                        this.config_.bandwidthDowngradeTarget;
-    let maxBandwidth = nextVariant.bandwidth /
+    const maxBandwidth = nextVariant.bandwidth /
                        this.config_.bandwidthUpgradeTarget;
     shaka.log.v2('Bandwidth ranges:',
                  (variant.bandwidth / 1e6).toFixed(3),
@@ -238,18 +238,18 @@ shaka.abr.SimpleAbrManager.prototype.suggestStreams_ = function() {
     this.startupComplete_ = true;
   } else {
     // Check if we've left the switch interval.
-    let now = Date.now();
-    let delta = now - this.lastTimeChosenMs_;
+    const now = Date.now();
+    const delta = now - this.lastTimeChosenMs_;
     if (delta < this.config_.switchInterval * 1000) {
       shaka.log.v2('Still within switch interval...');
       return;
     }
   }
 
-  let chosenVariant = this.chooseVariant();
-  let bandwidthEstimate = this.bandwidthEstimator_.getBandwidthEstimate(
+  const chosenVariant = this.chooseVariant();
+  const bandwidthEstimate = this.bandwidthEstimator_.getBandwidthEstimate(
       this.config_.defaultBandwidthEstimate);
-  let currentBandwidthKbps = Math.round(bandwidthEstimate / 1000.0);
+  const currentBandwidthKbps = Math.round(bandwidthEstimate / 1000.0);
 
   shaka.log.debug(
       'Calling switch_(), bandwidth=' + currentBandwidthKbps + ' kbps');