switch let to const when possible

.eslintrc

@@ -46,6 +46,7 @@
     "no-useless-call": 2,
     "no-useless-concat": 2,
     "no-warning-comments": [2, { "terms": ["do not submit"], "location": "anywhere" }],
+    "prefer-const": 2,
     "radix": 2,
     "semi": 2,
     "space-after-keywords": 2,

build-system/tasks/lint.js

@@ -53,7 +53,7 @@ function lint() {
   }
 
   return stream.pipe(eslint(options))
-    .pipe(eslint.formatEach('compact', function(msg) {
+    .pipe(eslint.formatEach('stylish', function(msg) {
       errorsFound = true;
       util.log(util.colors.red(msg));
     }))

builtins/amp-ad.js

@@ -63,15 +63,15 @@ const POSITION_FIXED_TAG_WHITELIST = {
  */
 export function scoreDimensions_(dims, maxWidth, maxHeight) {
   return dims.map(function(dim) {
-    let width = dim[0];
-    let height = dim[1];
-    let widthScore = Math.abs(width - maxWidth);
+    const width = dim[0];
+    const height = dim[1];
+    const widthScore = Math.abs(width - maxWidth);
     // if the width is over the max then we need to penalize it
-    let widthPenalty = Math.abs((maxWidth - width) * 3);
+    const widthPenalty = Math.abs((maxWidth - width) * 3);
     // we add a multiplier to height as we prioritize it more than width
-    let heightScore = Math.abs(height - maxHeight) * 2;
+    const heightScore = Math.abs(height - maxHeight) * 2;
     // if the height is over the max then we need to penalize it
-    let heightPenalty = Math.abs((maxHeight - height) * 2.5);
+    const heightPenalty = Math.abs((maxHeight - height) * 2.5);
 
     return (widthScore - widthPenalty) + (heightScore - heightPenalty);
   });
@@ -84,7 +84,7 @@ export function scoreDimensions_(dims, maxWidth, maxHeight) {
  */
 export function upgradeImages_(images) {
   Object.keys(images).forEach(key => {
-    let curDimImgs = images[key];
+    const curDimImgs = images[key];
     curDimImgs.forEach((item, index) => {
       curDimImgs[index] = item.replace(/@1x\.png$/, '@2x.png');
     });
@@ -148,9 +148,9 @@ export function installAd(win) {
     prefetchAd_() {
       // We always need the bootstrap.
       prefetchBootstrap(this.getWin());
-      let type = this.element.getAttribute('type');
-      let prefetch = adPrefetch[type];
-      let preconnect = adPreconnect[type];
+      const type = this.element.getAttribute('type');
+      const prefetch = adPrefetch[type];
+      const preconnect = adPreconnect[type];
       if (typeof prefetch == 'string') {
         this.preconnect.prefetch(prefetch);
       } else if (prefetch) {
@@ -166,7 +166,7 @@ export function installAd(win) {
         });
       }
       // If fully qualified src for ad script is specified we prefetch that.
-      let src = this.element.getAttribute('src');
+      const src = this.element.getAttribute('src');
       if (src) {
         this.preconnect.prefetch(src);
       }
@@ -187,7 +187,7 @@ export function installAd(win) {
      */
     isPositionFixed() {
       let el = this.element;
-      let body = el.ownerDocument.body;
+      const body = el.ownerDocument.body;
       do {
         if (POSITION_FIXED_TAG_WHITELIST[el.tagName]) {
           return false;
@@ -248,7 +248,7 @@ export function installAd(win) {
         margin: 'auto',
       });
 
-      let winner = this.getPlaceholderImage_();
+      const winner = this.getPlaceholderImage_();
       img.src = `https://ampproject.org/backfill/${winner}`;
       this.placeholder_ = a;
       a.appendChild(img);
@@ -261,12 +261,12 @@ export function installAd(win) {
      * @return {string} The image URL.
      */
     getPlaceholderImage_() {
-      let scores = scoreDimensions_(BACKFILL_DIMENSIONS_,
+      const scores = scoreDimensions_(BACKFILL_DIMENSIONS_,
           this.element./*REVIEW*/clientWidth,
           this.element./*REVIEW*/clientHeight);
-      let dims = BACKFILL_DIMENSIONS_[
+      const dims = BACKFILL_DIMENSIONS_[
           scores.indexOf(Math.max.apply(Math, scores))];
-      let images = BACKFILL_IMGS_[dims.join('x')];
+      const images = BACKFILL_IMGS_[dims.join('x')];
       // do we need a more sophisticated randomizer?
       return images[Math.floor(Math.random() * images.length)];
     }

builtins/amp-img.js

@@ -82,7 +82,7 @@ export function installImg(win) {
       if (this.getLayoutWidth() <= 0) {
         return Promise.resolve();
       }
-      let src = this.srcset_.select(this.getLayoutWidth(), this.getDpr()).url;
+      const src = this.srcset_.select(this.getLayoutWidth(), this.getDpr()).url;
       if (src == this.img_.getAttribute('src')) {
         return Promise.resolve();
       }

builtins/amp-pixel.js

@@ -51,15 +51,15 @@ export function installPixel(win) {
      * Returns the host of the canonical URL for this AMP document.
      */
     'CANONICAL_HOST': () => {
-      let url = parseUrl(documentInfoFor(win).canonicalUrl);
+      const url = parseUrl(documentInfoFor(win).canonicalUrl);
       return url && url.hostname;
     },
 
     /**
      * Returns the path of the canonical URL for this AMP document.
      */
     'CANONICAL_PATH': () => {
-      let url = parseUrl(documentInfoFor(win).canonicalUrl);
+      const url = parseUrl(documentInfoFor(win).canonicalUrl);
       return url && url.pathname;
     },
 
@@ -88,7 +88,7 @@ export function installPixel(win) {
      * Returns the host of the URL for this AMP document.
      */
     'AMPDOC_HOST': () => {
-      let url = parseUrl(win.location.href);
+      const url = parseUrl(win.location.href);
       return url && url.hostname;
     }
   };
@@ -98,7 +98,7 @@ export function installPixel(win) {
    */
   const REPLACEMENT_EXPR = (() => {
     let all = '';
-    for (let k in REPLACEMENTS) {
+    for (const k in REPLACEMENTS) {
       all += (all.length > 0 ? '|' : '') + k;
     }
     return new RegExp('\\$(' + all + ')', 'g');

builtins/amp-video.js

@@ -37,9 +37,9 @@ export function installVideo(win) {
 
     /** @override */
     layoutCallback() {
-      let width = this.element.getAttribute('width');
-      let height = this.element.getAttribute('height');
-      let video = document.createElement('video');
+      const width = this.element.getAttribute('width');
+      const height = this.element.getAttribute('height');
+      const video = document.createElement('video');
       if (!video.play) {
         this.toggleFallback(true);
         return Promise.resolve();

extensions/amp-anim/0.1/amp-anim.js

@@ -86,7 +86,7 @@ class AmpAnim extends AMP.BaseElement {
 
   /** @private */
   updateInViewport_() {
-    let inViewport = this.isInViewport();
+    const inViewport = this.isInViewport();
     this.togglePlaceholder(!inViewport);
     st.toggle(this.img_, inViewport);
   }
@@ -99,7 +99,7 @@ class AmpAnim extends AMP.BaseElement {
     if (this.getLayoutWidth() <= 0) {
       return Promise.resolve();
     }
-    let src = this.srcset_.select(this.getLayoutWidth(),
+    const src = this.srcset_.select(this.getLayoutWidth(),
         this.getDpr()).url;
     if (src == this.img_.getAttribute('src')) {
       return Promise.resolve();

extensions/amp-audio/0.1/amp-audio.js

@@ -31,7 +31,7 @@ export class AmpAudio extends AMP.BaseElement {
 
   /** @override */
   layoutCallback() {
-    let audio = document.createElement('audio');
+    const audio = document.createElement('audio');
     if (!audio.play) {
       this.toggleFallback(true);
       return Promise.resolve();

extensions/amp-audio/0.1/test/test-amp-audio.js

@@ -53,7 +53,7 @@ describe('amp-audio', () => {
           child = iframe.doc.createTextNode(childNodeAttrs.text);
         } else {
           child = iframe.doc.createElement(childNodeAttrs.tag);
-          for (let key in childNodeAttrs) {
+          for (const key in childNodeAttrs) {
             if (key !== 'tag') {
               child.setAttribute(key, childNodeAttrs[key]);
             }
@@ -148,17 +148,17 @@ describe('amp-audio', () => {
   });
 
   it('should fallback when not available', () => {
-    let savedCreateElement = document.createElement;
+    const savedCreateElement = document.createElement;
     document.createElement = name => {
       if (name == 'audio') {
         return savedCreateElement.call(document, 'audio2');
       }
       return savedCreateElement.call(document, name);
     };
-    let element = document.createElement('div');
+    const element = document.createElement('div');
     element.toggleFallback = sinon.spy();
-    let audio = new AmpAudio(element);
-    let promise = audio.layoutCallback();
+    const audio = new AmpAudio(element);
+    const promise = audio.layoutCallback();
     document.createElement = savedCreateElement;
     return promise.then(() => {
       expect(audio.audio_).to.be.undefined;

extensions/amp-carousel/0.1/carousel.js

@@ -115,9 +115,9 @@ export class AmpCarousel extends BaseCarousel {
    * @private
    */
   nextPos_(pos, dir) {
-    let containerWidth = this.element./*OK*/offsetWidth;
-    let fullWidth = this.container_./*OK*/scrollWidth;
-    let newPos = pos + dir * containerWidth;
+    const containerWidth = this.element./*OK*/offsetWidth;
+    const fullWidth = this.container_./*OK*/scrollWidth;
+    const newPos = pos + dir * containerWidth;
     if (newPos < 0) {
       return 0;
     }
@@ -134,9 +134,9 @@ export class AmpCarousel extends BaseCarousel {
    * @private
    */
   withinWindow_(pos, callback) {
-    let containerWidth = this.getLayoutWidth();
+    const containerWidth = this.getLayoutWidth();
     for (let i = 0; i < this.cells_.length; i++) {
-      let cell = this.cells_[i];
+      const cell = this.cells_[i];
       if (cell./*OK*/offsetLeft + cell./*OK*/offsetWidth >= pos &&
             cell./*OK*/offsetLeft <= pos + containerWidth) {
         callback(cell);
@@ -174,7 +174,7 @@ export class AmpCarousel extends BaseCarousel {
    * @private
    */
   updateInViewport_(newPos, oldPos) {
-    let seen = [];
+    const seen = [];
     this.withinWindow_(newPos, cell => {
       seen.push(cell);
       this.updateInViewport(cell, true);
@@ -201,7 +201,7 @@ export class AmpCarousel extends BaseCarousel {
     /** @private {?Motion} */
     this.motion_ = null;
 
-    let gestures = Gestures.get(this.element);
+    const gestures = Gestures.get(this.element);
     gestures.onGesture(SwipeXRecognizer, e => {
       if (e.data.first) {
         this.onSwipeStart_(e.data);
@@ -253,7 +253,7 @@ export class AmpCarousel extends BaseCarousel {
     if (Math.abs(swipe.velocityX) > 0.1) {
       this.motion_ = continueMotion(this.pos_, 0, -swipe.velocityX, 0,
           (x, y) => {
-            let newPos = (this.boundPos_(x, true) +
+            const newPos = (this.boundPos_(x, true) +
                 this.boundPos_(x, false)) * 0.5;
             if (Math.abs(newPos - this.pos_) <= 1) {
               // Hit the wall: stop motion.
@@ -270,11 +270,11 @@ export class AmpCarousel extends BaseCarousel {
       promise = Promise.resolve();
     }
     return promise.then(() => {
-      let newPos = this.boundPos_(this.pos_, false);
+      const newPos = this.boundPos_(this.pos_, false);
       if (Math.abs(newPos - this.pos_) < 1) {
         return undefined;
       }
-      let posFunc = tr.numeric(this.pos_, newPos);
+      const posFunc = tr.numeric(this.pos_, newPos);
       return Animation.animate(time => {
         this.pos_ = posFunc(time);
         st.setStyles(this.container_, {
@@ -290,8 +290,8 @@ export class AmpCarousel extends BaseCarousel {
 
   /** @private */
   updateBounds_() {
-    let containerWidth = this.element./*OK*/offsetWidth;
-    let scrollWidth = this.container_./*OK*/scrollWidth;
+    const containerWidth = this.element./*OK*/offsetWidth;
+    const scrollWidth = this.container_./*OK*/scrollWidth;
     this.minPos_ = 0;
     this.maxPos_ = Math.max(scrollWidth - containerWidth, 0);
     this.extent_ = Math.min(containerWidth * 0.4, 200);
@@ -304,7 +304,7 @@ export class AmpCarousel extends BaseCarousel {
    * @private
    */
   boundPos_(pos, allowExtent) {
-    let extent = allowExtent ? this.extent_ : 0;
+    const extent = allowExtent ? this.extent_ : 0;
     return Math.min(this.maxPos_ + extent,
         Math.max(this.minPos_ - extent, pos));
   }
@@ -316,9 +316,9 @@ export class AmpCarousel extends BaseCarousel {
 
   /** @override */
   hasNext() {
-    let containerWidth = this.getLayoutWidth();
-    let scrollWidth = this.container_./*OK*/scrollWidth;
-    let maxPos = Math.max(scrollWidth - containerWidth, 0);
+    const containerWidth = this.getLayoutWidth();
+    const scrollWidth = this.container_./*OK*/scrollWidth;
+    const maxPos = Math.max(scrollWidth - containerWidth, 0);
     return this.pos_ != maxPos;
   }
 }