perf: Various small performance improvements. (#4426)

These are a few performance improvements.

* Use textContent instead of innerHTML for text content.
* Construct TextTrackSettings content with HTML strings where possible because it's a bit faster than manual DOM construction.
* Do minimal DOM updates to time controls. This reduces our timeupdate footprint from ~2-2.5ms to ~1ms!

src/js/clickable-component.js

@@ -120,7 +120,7 @@ class ClickableComponent extends Component {
     const localizedText = this.localize(text);
 
     this.controlText_ = text;
-    this.controlTextEl_.innerHTML = localizedText;
+    Dom.textContent(this.controlTextEl_, localizedText);
     if (!this.nonIconControl) {
       // Set title attribute if only an icon is shown
       el.setAttribute('title', localizedText);

src/js/control-bar/time-controls/current-time-display.js

@@ -1,8 +1,10 @@
 /**
  * @file current-time-display.js
  */
+import document from 'global/document';
 import Component from '../../component.js';
 import * as Dom from '../../utils/dom.js';
+import {bind, throttle} from '../../utils/fn.js';
 import formatTime from '../../utils/format-time.js';
 
 /**
@@ -23,8 +25,8 @@ class CurrentTimeDisplay extends Component {
    */
   constructor(player, options) {
     super(player, options);
-
+    this.throttledUpdateContent = throttle(bind(this, this.updateContent), 25);
-    this.on(player, 'timeupdate', this.updateContent);
+    this.on(player, 'timeupdate', this.throttledUpdateContent);
   }
 
   /**
@@ -39,18 +41,34 @@ class CurrentTimeDisplay extends Component {
     });
 
     this.contentEl_ = Dom.createEl('div', {
-      className: 'vjs-current-time-display',
+      className: 'vjs-current-time-display'
-      // label the current time for screen reader users
-      innerHTML: '<span class="vjs-control-text">Current Time </span>' + '0:00'
     }, {
       // tell screen readers not to automatically read the time as it changes
       'aria-live': 'off'
-    });
+    }, Dom.createEl('span', {
+      className: 'vjs-control-text',
+      textContent: this.localize('Current Time')
+    }));
 
+    this.updateTextNode_();
     el.appendChild(this.contentEl_);
     return el;
   }
 
+  /**
+   * Updates the "current time" text node with new content using the
+   * contents of the `formattedTime_` property.
+   *
+   * @private
+   */
+  updateTextNode_() {
+    if (this.textNode_) {
+      this.contentEl_.removeChild(this.textNode_);
+    }
+    this.textNode_ = document.createTextNode(` ${this.formattedTime_ || '0:00'}`);
+    this.contentEl_.appendChild(this.textNode_);
+  }
+
   /**
    * Update current time display
    *
@@ -62,12 +80,11 @@ class CurrentTimeDisplay extends Component {
   updateContent(event) {
     // Allows for smooth scrubbing, when player can't keep up.
     const time = (this.player_.scrubbing()) ? this.player_.getCache().currentTime : this.player_.currentTime();
-    const localizedText = this.localize('Current Time');
     const formattedTime = formatTime(time, this.player_.duration());
 
     if (formattedTime !== this.formattedTime_) {
       this.formattedTime_ = formattedTime;
-      this.contentEl_.innerHTML = `<span class="vjs-control-text">${localizedText}</span> ${formattedTime}`;
+      this.requestAnimationFrame(this.updateTextNode_);
     }
   }
 

src/js/control-bar/time-controls/duration-display.js

@@ -1,8 +1,10 @@
 /**
  * @file duration-display.js
  */
+import document from 'global/document';
 import Component from '../../component.js';
 import * as Dom from '../../utils/dom.js';
+import {bind, throttle} from '../../utils/fn.js';
 import formatTime from '../../utils/format-time.js';
 
 /**
@@ -24,13 +26,17 @@ class DurationDisplay extends Component {
   constructor(player, options) {
     super(player, options);
 
-    this.on(player, 'durationchange', this.updateContent);
+    this.throttledUpdateContent = throttle(bind(this, this.updateContent), 25);
 
-    // Also listen for timeupdate and loadedmetadata because removing those
+    this.on(player, [
-    // listeners could have broken dependent applications/libraries. These
+      'durationchange',
-    // can likely be removed for 6.0.
+
-    this.on(player, 'timeupdate', this.updateContent);
+      // Also listen for timeupdate and loadedmetadata because removing those
-    this.on(player, 'loadedmetadata', this.updateContent);
+      // listeners could have broken dependent applications/libraries. These
+      // can likely be removed for 7.0.
+      'loadedmetadata',
+      'timeupdate'
+    ], this.throttledUpdateContent);
   }
 
   /**
@@ -45,18 +51,34 @@ class DurationDisplay extends Component {
     });
 
     this.contentEl_ = Dom.createEl('div', {
-      className: 'vjs-duration-display',
+      className: 'vjs-duration-display'
-      // label the duration time for screen reader users
-      innerHTML: `<span class="vjs-control-text">${this.localize('Duration Time')}</span> 0:00`
     }, {
       // tell screen readers not to automatically read the time as it changes
       'aria-live': 'off'
-    });
+    }, Dom.createEl('span', {
+      className: 'vjs-control-text',
+      textContent: this.localize('Duration Time')
+    }));
 
+    this.updateTextNode_();
     el.appendChild(this.contentEl_);
     return el;
   }
 
+  /**
+   * Updates the "current time" text node with new content using the
+   * contents of the `formattedTime_` property.
+   *
+   * @private
+   */
+  updateTextNode_() {
+    if (this.textNode_) {
+      this.contentEl_.removeChild(this.textNode_);
+    }
+    this.textNode_ = document.createTextNode(` ${this.formattedTime_ || '0:00'}`);
+    this.contentEl_.appendChild(this.textNode_);
+  }
+
   /**
    * Update duration time display.
    *
@@ -73,14 +95,10 @@ class DurationDisplay extends Component {
 
     if (duration && this.duration_ !== duration) {
       this.duration_ = duration;
-      const localizedText = this.localize('Duration Time');
+      this.formattedTime_ = formatTime(duration);
-      const formattedTime = formatTime(duration);
+      this.requestAnimationFrame(this.updateTextNode_);
-
-      // label the duration time for screen reader users
-      this.contentEl_.innerHTML = `<span class="vjs-control-text">${localizedText}</span> ${formattedTime}`;
     }
   }
-
 }
 
 Component.registerComponent('DurationDisplay', DurationDisplay);

src/js/control-bar/time-controls/remaining-time-display.js

@@ -1,8 +1,10 @@
 /**
  * @file remaining-time-display.js
  */
+import document from 'global/document';
 import Component from '../../component.js';
 import * as Dom from '../../utils/dom.js';
+import {bind, throttle} from '../../utils/fn.js';
 import formatTime from '../../utils/format-time.js';
 
 /**
@@ -23,9 +25,8 @@ class RemainingTimeDisplay extends Component {
    */
   constructor(player, options) {
     super(player, options);
-
+    this.throttledUpdateContent = throttle(bind(this, this.updateContent), 25);
-    this.on(player, 'timeupdate', this.updateContent);
+    this.on(player, ['timeupdate', 'durationchange'], this.throttledUpdateContent);
-    this.on(player, 'durationchange', this.updateContent);
   }
 
   /**
@@ -40,18 +41,34 @@ class RemainingTimeDisplay extends Component {
     });
 
     this.contentEl_ = Dom.createEl('div', {
-      className: 'vjs-remaining-time-display',
+      className: 'vjs-remaining-time-display'
-      // label the remaining time for screen reader users
-      innerHTML: `<span class="vjs-control-text">${this.localize('Remaining Time')}</span> -0:00`
     }, {
       // tell screen readers not to automatically read the time as it changes
       'aria-live': 'off'
-    });
+    }, Dom.createEl('span', {
+      className: 'vjs-control-text',
+      textContent: this.localize('Remaining Time')
+    }));
 
+    this.updateTextNode_();
     el.appendChild(this.contentEl_);
     return el;
   }
 
+  /**
+   * Updates the "remaining time" text node with new content using the
+   * contents of the `formattedTime_` property.
+   *
+   * @private
+   */
+  updateTextNode_() {
+    if (this.textNode_) {
+      this.contentEl_.removeChild(this.textNode_);
+    }
+    this.textNode_ = document.createTextNode(` -${this.formattedTime_ || '0:00'}`);
+    this.contentEl_.appendChild(this.textNode_);
+  }
+
   /**
    * Update remaining time display.
    *
@@ -63,20 +80,14 @@ class RemainingTimeDisplay extends Component {
    */
   updateContent(event) {
     if (this.player_.duration()) {
-      const localizedText = this.localize('Remaining Time');
       const formattedTime = formatTime(this.player_.remainingTime());
 
       if (formattedTime !== this.formattedTime_) {
         this.formattedTime_ = formattedTime;
-        this.contentEl_.innerHTML = `<span class="vjs-control-text">${localizedText}</span> -${formattedTime}`;
+        this.requestAnimationFrame(this.updateTextNode_);
       }
     }
-
-    // Allows for smooth scrubbing, when player can't keep up.
-    // var time = (this.player_.scrubbing()) ? this.player_.getCache().currentTime : this.player_.currentTime();
-    // this.contentEl_.innerHTML = vjs.formatTime(time, this.player_.duration());
   }
-
 }
 
 Component.registerComponent('RemainingTimeDisplay', RemainingTimeDisplay);

src/js/tech/html5.js

@@ -368,24 +368,26 @@ class Html5 extends Tech {
     // playback has started, which triggers the live display erroneously.
     // Return NaN if playback has not started and trigger a durationupdate once
     // the duration can be reliably known.
-    if (this.el_.duration === Infinity &&
+    if (
-      browser.IS_ANDROID && browser.IS_CHROME) {
+      this.el_.duration === Infinity &&
-      if (this.el_.currentTime === 0) {
+      browser.IS_ANDROID &&
-        // Wait for the first `timeupdate` with currentTime > 0 - there may be
+      browser.IS_CHROME &&
-        // several with 0
+      this.el_.currentTime === 0
-        const checkProgress = () => {
+    ) {
-          if (this.el_.currentTime > 0) {
+      // Wait for the first `timeupdate` with currentTime > 0 - there may be
-            // Trigger durationchange for genuinely live video
+      // several with 0
-            if (this.el_.duration === Infinity) {
+      const checkProgress = () => {
-              this.trigger('durationchange');
+        if (this.el_.currentTime > 0) {
-            }
+          // Trigger durationchange for genuinely live video
-            this.off('timeupdate', checkProgress);
+          if (this.el_.duration === Infinity) {
+            this.trigger('durationchange');
           }
-        };
+          this.off('timeupdate', checkProgress);
+        }
+      };
 
-        this.on('timeupdate', checkProgress);
+      this.on('timeupdate', checkProgress);
-        return NaN;
+      return NaN;
-      }
     }
     return this.el_.duration || NaN;
   }

src/js/tracks/text-track-settings.js

@@ -299,8 +299,9 @@ class TextTrackSettings extends ModalDialog {
    * @param {string} key
    *        Configuration key to use during creation.
    *
-   * @return {Element}
+   * @return {string}
-   *         The DOM element that gets created.
+   *         An HTML string.
+   *
    * @private
    */
   createElSelect_(key, legendId = '', type = 'label') {
@@ -308,101 +309,94 @@ class TextTrackSettings extends ModalDialog {
     const id = config.id.replace('%s', this.id_);
 
     return [
-      createEl(type, {
+      `<${type} id="${id}" class="${type === 'label' ? 'vjs-label' : ''}">`,
-        id,
+      this.localize(config.label),
-        className: type === 'label' ? 'vjs-label' : '',
+      `</${type}>`,
-        textContent: this.localize(config.label)
+      `<select aria-labelledby="${legendId} ${id}">`
-      }, {
+    ].
-      }),
+      concat(config.options.map(o => {
-      createEl('select', {}, {
-        'aria-labelledby': `${legendId} ${id}`
-      }, config.options.map(o => {
         const optionId = id + '-' + o[1];
 
-        return createEl('option', {
+        return [
-          id: optionId,
+          `<option id="${optionId}" value="${o[0]}" `,
-          textContent: this.localize(o[1]),
+          `aria-labelledby="${legendId} ${id} ${optionId}">`,
-          value: o[0]
+          this.localize(o[1]),
-        }, {
+          '</option>'
-          'aria-labelledby': `${legendId} ${id} ${optionId}`
+        ].join('');
-        });
+      })).
-      }))
+      concat('</select>').join('');
-    ];
   }
 
   /**
    * Create foreground color element for the component
    *
-   * @return {Element}
+   * @return {string}
-   *         The element that was created.
+   *         An HTML string.
    *
    * @private
    */
   createElFgColor_() {
-    const legend = createEl('legend', {
+    const legendId = `captions-text-legend-${this.id_}`;
-      id: `captions-text-legend-${this.id_}`,
-      textContent: this.localize('Text')
-    });
 
-    const select = this.createElSelect_('color', legend.id);
+    return [
-
+      '<fieldset class="vjs-fg-color vjs-track-setting">',
-    const opacity = createEl('span', {
+      `<legend id="${legendId}">`,
-      className: 'vjs-text-opacity vjs-opacity'
+      this.localize('Text'),
-    }, undefined, this.createElSelect_('textOpacity', legend.id));
+      '</legend>',
-
+      this.createElSelect_('color', legendId),
-    return createEl('fieldset', {
+      '<span class="vjs-text-opacity vjs-opacity">',
-      className: 'vjs-fg-color vjs-track-setting'
+      this.createElSelect_('textOpacity', legendId),
-    }, undefined, [legend].concat(select, opacity));
+      '</span>',
+      '</fieldset>'
+    ].join('');
   }
 
   /**
    * Create background color element for the component
    *
-   * @return {Element}
+   * @return {string}
-   *         The element that was created
+   *         An HTML string.
    *
    * @private
    */
   createElBgColor_() {
-    const legend = createEl('legend', {
+    const legendId = `captions-background-${this.id_}`;
-      id: `captions-background-${this.id_}`,
-      textContent: this.localize('Background')
-    });
 
-    const select = this.createElSelect_('backgroundColor', legend.id);
+    return [
-
+      '<fieldset class="vjs-bg-color vjs-track-setting">',
-    const opacity = createEl('span', {
+      `<legend id="${legendId}">`,
-      className: 'vjs-bg-opacity vjs-opacity'
+      this.localize('Background'),
-    }, undefined, this.createElSelect_('backgroundOpacity', legend.id));
+      '</legend>',
-
+      this.createElSelect_('backgroundColor', legendId),
-    return createEl('fieldset', {
+      '<span class="vjs-bg-opacity vjs-opacity">',
-      className: 'vjs-bg-color vjs-track-setting'
+      this.createElSelect_('backgroundOpacity', legendId),
-    }, undefined, [legend].concat(select, opacity));
+      '</span>',
+      '</fieldset>'
+    ].join('');
   }
 
   /**
    * Create window color element for the component
    *
-   * @return {Element}
+   * @return {string}
-   *         The element that was created
+   *         An HTML string.
    *
    * @private
    */
   createElWinColor_() {
-    const legend = createEl('legend', {
+    const legendId = `captions-window-${this.id_}`;
-      id: `captions-window-${this.id_}`,
-      textContent: this.localize('Window')
-    });
 
-    const select = this.createElSelect_('windowColor', legend.id);
+    return [
-
+      '<fieldset class="vjs-window-color vjs-track-setting">',
-    const opacity = createEl('span', {
+      `<legend id="${legendId}">`,
-      className: 'vjs-window-opacity vjs-opacity'
+      this.localize('Window'),
-    }, undefined, this.createElSelect_('windowOpacity', legend.id));
+      '</legend>',
-
+      this.createElSelect_('windowColor', legendId),
-    return createEl('fieldset', {
+      '<span class="vjs-window-opacity vjs-opacity">',
-      className: 'vjs-window-color vjs-track-setting'
+      this.createElSelect_('windowOpacity', legendId),
-    }, undefined, [legend].concat(select, opacity));
+      '</span>',
+      '</fieldset>'
+    ].join('');
   }
 
   /**
@@ -415,12 +409,13 @@ class TextTrackSettings extends ModalDialog {
    */
   createElColors_() {
     return createEl('div', {
-      className: 'vjs-track-settings-colors'
+      className: 'vjs-track-settings-colors',
-    }, undefined, [
+      innerHTML: [
-      this.createElFgColor_(),
+        this.createElFgColor_(),
-      this.createElBgColor_(),
+        this.createElBgColor_(),
-      this.createElWinColor_()
+        this.createElWinColor_()
-    ]);
+      ].join('')
+    });
   }
 
   /**
@@ -432,21 +427,20 @@ class TextTrackSettings extends ModalDialog {
    * @private
    */
   createElFont_() {
-    const fontPercent = createEl('fieldset', {
-      className: 'vjs-font-percent vjs-track-setting'
-    }, undefined, this.createElSelect_('fontPercent', '', 'legend'));
-
-    const edgeStyle = createEl('fieldset', {
-      className: 'vjs-edge-style vjs-track-setting'
-    }, undefined, this.createElSelect_('edgeStyle', '', 'legend'));
-
-    const fontFamily = createEl('fieldset', {
-      className: 'vjs-font-family vjs-track-setting'
-    }, undefined, this.createElSelect_('fontFamily', '', 'legend'));
-
     return createEl('div', {
-      className: 'vjs-track-settings-font'
+      className: 'vjs-track-settings-font">',
-    }, undefined, [fontPercent, edgeStyle, fontFamily]);
+      innerHTML: [
+        '<fieldset class="vjs-font-percent vjs-track-setting">',
+        this.createElSelect_('fontPercent', '', 'legend'),
+        '</fieldset>',
+        '<fieldset class="vjs-edge-style vjs-track-setting">',
+        this.createElSelect_('edgeStyle', '', 'legend'),
+        '</fieldset>',
+        '<fieldset class="vjs-font-family vjs-track-setting">',
+        this.createElSelect_('fontFamily', '', 'legend'),
+        '</fieldset>'
+      ].join('')
+    });
   }
 
   /**
@@ -459,30 +453,17 @@ class TextTrackSettings extends ModalDialog {
    */
   createElControls_() {
     const defaultsDescription = this.localize('restore all settings to the default values');
-    const defaultsButton = createEl('button', {
-      className: 'vjs-default-button',
-      title: defaultsDescription,
-      innerHTML: `${this.localize('Reset')}<span class='vjs-control-text'> ${defaultsDescription}</span>`
-    });
-
-    const doneButton = createEl('button', {
-      className: 'vjs-done-button',
-      textContent: this.localize('Done')
-    });
 
     return createEl('div', {
-      className: 'vjs-track-settings-controls'
+      className: 'vjs-track-settings-controls',
-    }, undefined, [defaultsButton, doneButton]);
+      innerHTML: [
-  }
+        `<button class="vjs-default-button" title="${defaultsDescription}">`,
-
+        this.localize('Reset'),
-  /**
+        `<span class="vjs-control-text"> ${defaultsDescription}</span>`,
-   * Create the component's DOM element
+        '</button>',
-   *
+        `<button class="vjs-done-button">${this.localize('Done')}</button>`
-   * @return {Element}
+      ].join('')
-   *         The element that was created.
+    });
-   */
-  createEl() {
-    return super.createEl();
   }
 
   content() {