Eslint rule updates (#673)

* Install unicorn

* Add rules

* Fix issues

* Install sonarjs

* Set up rules

* Fix issues

* Install eslint-plugin-import and fix import extensions

* Simplify permitted error names

44 files changed, 127 insertions, 131 deletions

diff --git a/ext/js/accessibility/google-docs-util.js b/ext/js/accessibility/google-docs-util.js
index 969e650e..31ae5982 100644
--- a/ext/js/accessibility/google-docs-util.js
+++ b/ext/js/accessibility/google-docs-util.js
@@ -86,6 +86,8 @@ export class GoogleDocsUtil {
         const content = document.createTextNode(text);
         const svgText = document.createElementNS('http://www.w3.org/2000/svg', 'text');
         const transform = element.getAttribute('transform') || '';
+        // Using getAttribute instead of dataset because element is an SVG element
+        // eslint-disable-next-line unicorn/prefer-dom-node-dataset
         const font = element.getAttribute('data-font-css') || '';
         const elementX = element.getAttribute('x');
         const elementY = element.getAttribute('y');
diff --git a/ext/js/app/frontend.js b/ext/js/app/frontend.js
index 27e7700e..84a8f1e6 100644
--- a/ext/js/app/frontend.js
+++ b/ext/js/app/frontend.js
@@ -82,9 +82,9 @@ export class Frontend {
         /** @type {?import('settings').ProfileOptions} */
         this._options = null;
         /** @type {number} */
-        this._pageZoomFactor = 1.0;
+        this._pageZoomFactor = 1;
         /** @type {number} */
-        this._contentScale = 1.0;
+        this._contentScale = 1;
         /** @type {Promise<void>} */
         this._lastShowPromise = Promise.resolve();
         /** @type {TextSourceGenerator} */
@@ -788,7 +788,7 @@ export class Frontend {
         }
         if (popupScaleRelativeToVisualViewport) {
             const {visualViewport} = window;
-            const visualViewportScale = (typeof visualViewport !== 'undefined' && visualViewport !== null ? visualViewport.scale : 1.0);
+            const visualViewportScale = (typeof visualViewport !== 'undefined' && visualViewport !== null ? visualViewport.scale : 1);
             contentScale /= visualViewportScale;
         }
         if (contentScale === this._contentScale) { return; }
diff --git a/ext/js/app/popup.js b/ext/js/app/popup.js
index 08ff0661..103a5468 100644
--- a/ext/js/app/popup.js
+++ b/ext/js/app/popup.js
@@ -68,7 +68,7 @@ export class Popup extends EventDispatcher {
         /** @type {?import('settings').OptionsContext} */
         this._optionsContext = null;
         /** @type {number} */
-        this._contentScale = 1.0;
+        this._contentScale = 1;
         /** @type {string} */
         this._targetOrigin = chrome.runtime.getURL('/').replace(/\/$/, '');
 
@@ -777,7 +777,7 @@ export class Popup extends EventDispatcher {
     _getPosition(sourceRects, writingMode, viewport) {
         sourceRects = this._convertSourceRectsCoordinateSpace(sourceRects);
         const contentScale = this._contentScale;
-        const scaleRatio = this._frameSizeContentScale === null ? 1.0 : contentScale / this._frameSizeContentScale;
+        const scaleRatio = this._frameSizeContentScale === null ? 1 : contentScale / this._frameSizeContentScale;
         this._frameSizeContentScale = contentScale;
         const frameRect = this._frame.getBoundingClientRect();
         const frameWidth = Math.max(frameRect.width * scaleRatio, this._initialWidth * contentScale);
@@ -1133,6 +1133,8 @@ class PopupError extends ExtensionError {
      */
     constructor(message, source) {
         super(message);
+        /** @type {string} */
+        this.name = 'PopupError';
         /** @type {Popup} */
         this._source = source;
     }
diff --git a/ext/js/app/theme-controller.js b/ext/js/app/theme-controller.js
index 559a6e57..384fbcc8 100644
--- a/ext/js/app/theme-controller.js
+++ b/ext/js/app/theme-controller.js
@@ -190,9 +190,9 @@ export class ThemeController {
         if (color === null) { return; }
 
         const a = color[3];
-        if (a <= 0.0) { return; }
+        if (a <= 0) { return; }
 
-        const aInv = 1.0 - a;
+        const aInv = 1 - a;
         for (let i = 0; i < 3; ++i) {
             target[i] = target[i] * aInv + color[i] * a;
         }
@@ -212,7 +212,7 @@ export class ThemeController {
             Number.parseInt(m[1], 10),
             Number.parseInt(m[2], 10),
             Number.parseInt(m[3], 10),
-            m4 ? Math.max(0.0, Math.min(1.0, Number.parseFloat(m4))) : 1.0
+            m4 ? Math.max(0, Math.min(1, Number.parseFloat(m4))) : 1
         ];
     }
 }
diff --git a/ext/js/background/backend.js b/ext/js/background/backend.js
index 090ba7b3..8ab56232 100644
--- a/ext/js/background/backend.js
+++ b/ext/js/background/backend.js
@@ -701,7 +701,7 @@ export class Backend {
                 typeof chrome.tabs.getZoom === 'function'
             )) {
                 // Not supported
-                resolve({zoomFactor: 1.0});
+                resolve({zoomFactor: 1});
                 return;
             }
             chrome.tabs.getZoom(tabId, (zoomFactor) => {
@@ -1701,10 +1701,8 @@ export class Backend {
                 // NOP
             }
 
-            if (okay && !done) {
-                if (add(item)) {
-                    done = true;
-                }
+            if (okay && !done && add(item)) {
+                done = true;
             }
         };
 
@@ -2294,7 +2292,7 @@ export class Backend {
      */
     _replaceInvalidFileNameCharacters(fileName) {
         // eslint-disable-next-line no-control-regex
-        return fileName.replace(/[<>:"/\\|?*\x00-\x1F]/g, '-');
+        return fileName.replace(/[<>:"/\\|?*\u0000-\u001F]/g, '-');
     }
 
     /**
diff --git a/ext/js/background/offscreen-proxy.js b/ext/js/background/offscreen-proxy.js
index 8c3f63c9..2351cb96 100644
--- a/ext/js/background/offscreen-proxy.js
+++ b/ext/js/background/offscreen-proxy.js
@@ -144,8 +144,7 @@ export class DictionaryDatabaseProxy {
      */
     async getMedia(targets) {
         const serializedMedia = /** @type {import('dictionary-database').Media<string>[]} */ (await this._offscreen.sendMessagePromise({action: 'databaseGetMediaOffscreen', params: {targets}}));
-        const media = serializedMedia.map((m) => ({...m, content: base64ToArrayBuffer(m.content)}));
-        return media;
+        return serializedMedia.map((m) => ({...m, content: base64ToArrayBuffer(m.content)}));
     }
 }
 
diff --git a/ext/js/background/offscreen.js b/ext/js/background/offscreen.js
index 754db517..dbdb9773 100644
--- a/ext/js/background/offscreen.js
+++ b/ext/js/background/offscreen.js
@@ -109,8 +109,7 @@ export class Offscreen {
     /** @type {import('offscreen').ApiHandler<'databaseGetMediaOffscreen'>} */
     async _getMediaHandler({targets}) {
         const media = await this._dictionaryDatabase.getMedia(targets);
-        const serializedMedia = media.map((m) => ({...m, content: arrayBufferToBase64(m.content)}));
-        return serializedMedia;
+        return media.map((m) => ({...m, content: arrayBufferToBase64(m.content)}));
     }
 
     /** @type {import('offscreen').ApiHandler<'translatorPrepareOffscreen'>} */
diff --git a/ext/js/core/extension-error.js b/ext/js/core/extension-error.js
index ab1c9dd7..6458f477 100644
--- a/ext/js/core/extension-error.js
+++ b/ext/js/core/extension-error.js
@@ -26,6 +26,8 @@ export class ExtensionError extends Error {
      */
     constructor(message) {
         super(message);
+        /** @type {string} */
+        this.name = 'ExtensionError';
         /** @type {unknown} */
         this._data = void 0;
     }
diff --git a/ext/js/data/json-schema.js b/ext/js/data/json-schema.js
index 3342e387..9e1497e9 100644
--- a/ext/js/data/json-schema.js
+++ b/ext/js/data/json-schema.js
@@ -27,6 +27,8 @@ export class JsonSchemaError extends Error {
      */
     constructor(message, valueStack, schemaStack) {
         super(message);
+        /** @type {string} */
+        this.name = 'JsonSchemaError';
         /** @type {import('ext/json-schema').ValueStackItem[]} */
         this._valueStack = valueStack;
         /** @type {import('ext/json-schema').SchemaStackItem[]} */
@@ -371,18 +373,16 @@ export class JsonSchema {
             return {schema, stack: [{schema, path: null}]};
         }
         const {prefixItems} = schema;
-        if (typeof prefixItems !== 'undefined') {
-            if (index >= 0 && index < prefixItems.length) {
-                const itemSchema = prefixItems[index];
-                if (typeof itemSchema !== 'undefined') {
-                    return {
-                        schema: itemSchema,
-                        stack: [
-                            {schema: prefixItems, path: 'prefixItems'},
-                            {schema: itemSchema, path: index}
-                        ]
-                    };
-                }
+        if (typeof prefixItems !== 'undefined' && index >= 0 && index < prefixItems.length) {
+            const itemSchema = prefixItems[index];
+            if (typeof itemSchema !== 'undefined') {
+                return {
+                    schema: itemSchema,
+                    stack: [
+                        {schema: prefixItems, path: 'prefixItems'},
+                        {schema: itemSchema, path: index}
+                    ]
+                };
             }
         }
         const {items} = schema;
diff --git a/ext/js/data/permissions-util.js b/ext/js/data/permissions-util.js
index 837b6d5f..097fe34d 100644
--- a/ext/js/data/permissions-util.js
+++ b/ext/js/data/permissions-util.js
@@ -113,10 +113,8 @@ export function getRequiredPermissionsForAnkiFieldValue(fieldValue) {
 export function hasRequiredPermissionsForOptions(permissions, options) {
     const permissionsSet = new Set(permissions.permissions);
 
-    if (!permissionsSet.has('nativeMessaging')) {
-        if (options.parsing.enableMecabParser) {
-            return false;
-        }
+    if (!permissionsSet.has('nativeMessaging') && options.parsing.enableMecabParser) {
+        return false;
     }
 
     if (!permissionsSet.has('clipboardRead')) {
diff --git a/ext/js/display/display-anki.js b/ext/js/display/display-anki.js
index 4766f1ae..d37efa85 100644
--- a/ext/js/display/display-anki.js
+++ b/ext/js/display/display-anki.js
@@ -953,6 +953,8 @@ class DisplayAnkiError extends Error {
      */
     constructor(message) {
         super(message);
+        /** @type {string} */
+        this.name = 'DisplayAnkiError';
         /** @type {?import('anki-note-builder').Requirement[]} */
         this._requirements = null;
         /** @type {?import('anki-note-builder').Requirement[]} */
diff --git a/ext/js/display/display-audio.js b/ext/js/display/display-audio.js
index 7d75d6b0..5f4131d0 100644
--- a/ext/js/display/display-audio.js
+++ b/ext/js/display/display-audio.js
@@ -33,7 +33,7 @@ export class DisplayAudio {
         /** @type {AudioSystem} */
         this._audioSystem = new AudioSystem();
         /** @type {number} */
-        this._playbackVolume = 1.0;
+        this._playbackVolume = 1;
         /** @type {boolean} */
         this._autoPlay = false;
         /** @type {?import('core').Timeout} */
@@ -166,7 +166,7 @@ export class DisplayAudio {
     _onOptionsUpdated({options}) {
         const {enabled, autoPlay, volume, sources} = options.audio;
         this._autoPlay = enabled && autoPlay;
-        this._playbackVolume = Number.isFinite(volume) ? Math.max(0.0, Math.min(1.0, volume / 100.0)) : 1.0;
+        this._playbackVolume = Number.isFinite(volume) ? Math.max(0, Math.min(1, volume / 100)) : 1;
 
         /** @type {Set<import('settings').AudioSourceType>} */
         const requiredAudioSources = new Set([
@@ -534,7 +534,7 @@ export class DisplayAudio {
         if (headwordNode !== null) {
             const {index} = headwordNode.dataset;
             if (typeof index === 'string') {
-                const headwordIndex = parseInt(index, 10);
+                const headwordIndex = Number.parseInt(index, 10);
                 if (Number.isFinite(headwordIndex)) { return headwordIndex; }
             }
         }
diff --git a/ext/js/display/display.js b/ext/js/display/display.js
index a5dad2d1..d30ed8a0 100644
--- a/ext/js/display/display.js
+++ b/ext/js/display/display.js
@@ -619,7 +619,7 @@ export class Display extends EventDispatcher {
         if (node === null) { return -1; }
         const {index} = node.dataset;
         if (typeof index !== 'string') { return -1; }
-        const indexNumber = parseInt(index, 10);
+        const indexNumber = Number.parseInt(index, 10);
         return Number.isFinite(indexNumber) ? indexNumber : -1;
     }
 
@@ -1020,7 +1020,7 @@ export class Display extends EventDispatcher {
         const node = /** @type {HTMLElement} */ (e.currentTarget);
         const {index} = node.dataset;
         if (typeof index !== 'string') { return; }
-        const indexNumber = parseInt(index, 10);
+        const indexNumber = Number.parseInt(index, 10);
         if (!Number.isFinite(indexNumber)) { return; }
         this._entrySetCurrent(indexNumber);
     }
@@ -1146,8 +1146,7 @@ export class Display extends EventDispatcher {
      */
     async _findDictionaryEntries(isKanji, source, wildcardsEnabled, optionsContext) {
         if (isKanji) {
-            const dictionaryEntries = await this._application.api.kanjiFind(source, optionsContext);
-            return dictionaryEntries;
+            return await this._application.api.kanjiFind(source, optionsContext);
         } else {
             /** @type {import('api').FindTermsDetails} */
             const findDetails = {};
@@ -1555,11 +1554,11 @@ export class Display extends EventDispatcher {
      * @returns {boolean}
      */
     _relativeTermView(next) {
-        if (next) {
-            return this._history.hasNext() && this._history.forward();
-        } else {
-            return this._history.hasPrevious() && this._history.back();
-        }
+        return (
+            next ?
+            this._history.hasNext() && this._history.forward() :
+            this._history.hasPrevious() && this._history.back()
+        );
     }
 
     /**
diff --git a/ext/js/display/element-overflow-controller.js b/ext/js/display/element-overflow-controller.js
index e0b9035e..eb83dda4 100644
--- a/ext/js/display/element-overflow-controller.js
+++ b/ext/js/display/element-overflow-controller.js
@@ -157,11 +157,11 @@ export class ElementOverflowController {
      * @returns {number|import('core').Timeout}
      */
     _requestIdleCallback(callback, timeout) {
-        if (typeof requestIdleCallback === 'function') {
-            return requestIdleCallback(callback, {timeout});
-        } else {
-            return setTimeout(callback, timeout);
-        }
+        return (
+            typeof requestIdleCallback === 'function' ?
+            requestIdleCallback(callback, {timeout}) :
+            setTimeout(callback, timeout)
+        );
     }
 
     /**
diff --git a/ext/js/display/sandbox/structured-content-generator.js b/ext/js/display/sandbox/structured-content-generator.js
index a04feaf2..1dfde39b 100644
--- a/ext/js/display/sandbox/structured-content-generator.js
+++ b/ext/js/display/sandbox/structured-content-generator.js
@@ -137,7 +137,7 @@ export class StructuredContentGenerator {
             imageContainer.title = title;
         }
 
-        aspectRatioSizer.style.paddingTop = `${invAspectRatio * 100.0}%`;
+        aspectRatioSizer.style.paddingTop = `${invAspectRatio * 100}%`;
 
         if (this._contentManager !== null) {
             this._contentManager.loadMedia(
diff --git a/ext/js/display/search-display-controller.js b/ext/js/display/search-display-controller.js
index ed2061e2..6767dce7 100644
--- a/ext/js/display/search-display-controller.js
+++ b/ext/js/display/search-display-controller.js
@@ -322,7 +322,7 @@ export class SearchDisplayController {
      */
     async _onProfileSelectChange(event) {
         const node = /** @type {HTMLInputElement} */ (event.currentTarget);
-        const value = parseInt(node.value, 10);
+        const value = Number.parseInt(node.value, 10);
         const optionsFull = await this._display.application.api.optionsGetFull();
         if (typeof value === 'number' && Number.isFinite(value) && value >= 0 && value <= optionsFull.profiles.length) {
             this._setPrimaryProfileIndex(value);
@@ -574,8 +574,7 @@ export class SearchDisplayController {
             case 'select':
                 return true;
         }
-        if (element instanceof HTMLElement && element.isContentEditable) { return true; }
-        return false;
+        return element instanceof HTMLElement && !!element.isContentEditable;
     }
 
     /**
diff --git a/ext/js/dom/document-util.js b/ext/js/dom/document-util.js
index 1ec699e6..a98bfe86 100644
--- a/ext/js/dom/document-util.js
+++ b/ext/js/dom/document-util.js
@@ -18,7 +18,9 @@
 
 /**
  * This class contains utility functions related to the HTML document.
+ * TODO : This class should be made non-static
  */
+// eslint-disable-next-line unicorn/no-static-only-class
 export class DocumentUtil {
     /** @type {?boolean} */
     static _cssZoomSupported = null;
@@ -460,7 +462,7 @@ export class DocumentUtil {
             if (typeof value !== 'string' || value.length === 0) {
                 return null;
             }
-            value = parseFloat(value);
+            value = Number.parseFloat(value);
         }
         return !Number.isNaN(value) ? value : null;
     }
diff --git a/ext/js/dom/dom-text-scanner.js b/ext/js/dom/dom-text-scanner.js
index f1dc3661..5b3ea564 100644
--- a/ext/js/dom/dom-text-scanner.js
+++ b/ext/js/dom/dom-text-scanner.js
@@ -488,8 +488,8 @@ export class DOMTextScanner {
     static isStyleVisible(style) {
         return !(
             style.visibility === 'hidden' ||
-            parseFloat(style.opacity) <= 0 ||
-            parseFloat(style.fontSize) <= 0 ||
+            Number.parseFloat(style.opacity) <= 0 ||
+            Number.parseFloat(style.fontSize) <= 0 ||
             (
                 !DOMTextScanner.isStyleSelectable(style) &&
                 (
diff --git a/ext/js/dom/panel-element.js b/ext/js/dom/panel-element.js
index 9c1289d7..0f2801e6 100644
--- a/ext/js/dom/panel-element.js
+++ b/ext/js/dom/panel-element.js
@@ -89,16 +89,14 @@ export class PanelElement extends EventDispatcher {
      * @param {(details: import('core').EventArgument<import('panel-element').Events, TName>) => void} callback
      */
     on(eventName, callback) {
-        if (eventName === 'visibilityChanged') {
-            if (this._mutationObserver === null) {
-                this._visible = this.isVisible();
-                this._mutationObserver = new MutationObserver(this._onMutation.bind(this));
-                this._mutationObserver.observe(this._node, {
-                    attributes: true,
-                    attributeFilter: ['hidden'],
-                    attributeOldValue: true
-                });
-            }
+        if (eventName === 'visibilityChanged' && this._mutationObserver === null) {
+            this._visible = this.isVisible();
+            this._mutationObserver = new MutationObserver(this._onMutation.bind(this));
+            this._mutationObserver.observe(this._node, {
+                attributes: true,
+                attributeFilter: ['hidden'],
+                attributeOldValue: true
+            });
         }
         super.on(eventName, callback);
     }
@@ -111,11 +109,9 @@ export class PanelElement extends EventDispatcher {
      */
     off(eventName, callback) {
         const result = super.off(eventName, callback);
-        if (eventName === 'visibilityChanged' && !this.hasListeners(eventName)) {
-            if (this._mutationObserver !== null) {
-                this._mutationObserver.disconnect();
-                this._mutationObserver = null;
-            }
+        if (eventName === 'visibilityChanged' && !this.hasListeners(eventName) && this._mutationObserver !== null) {
+            this._mutationObserver.disconnect();
+            this._mutationObserver = null;
         }
         return result;
     }
diff --git a/ext/js/dom/popup-menu.js b/ext/js/dom/popup-menu.js
index 8a8a19ba..28bcc309 100644
--- a/ext/js/dom/popup-menu.js
+++ b/ext/js/dom/popup-menu.js
@@ -219,8 +219,8 @@ export class PopupMenu extends EventDispatcher {
             (bottom - top) * ((-vertical + 1) * -0.5)
         );
 
-        x = Math.max(0.0, Math.min(containerNodeRect.width - menuRect.width, x));
-        y = Math.max(0.0, Math.min(containerNodeRect.height - menuRect.height, y));
+        x = Math.max(0, Math.min(containerNodeRect.width - menuRect.width, x));
+        y = Math.max(0, Math.min(containerNodeRect.height - menuRect.height, y));
 
         menu.style.left = `${x}px`;
         menu.style.top = `${y}px`;
diff --git a/ext/js/dom/scroll-element.js b/ext/js/dom/scroll-element.js
index 8005469b..7cd00f01 100644
--- a/ext/js/dom/scroll-element.js
+++ b/ext/js/dom/scroll-element.js
@@ -133,10 +133,10 @@ export class ScrollElement {
      */
     _easeInOutCubic(t) {
         if (t < 0.5) {
-            return (4.0 * t * t * t);
+            return (4 * t * t * t);
         } else {
-            t = 1.0 - t;
-            return 1.0 - (4.0 * t * t * t);
+            t = 1 - t;
+            return 1 - (4 * t * t * t);
         }
     }
 
diff --git a/ext/js/dom/selector-observer.js b/ext/js/dom/selector-observer.js
index 791ce627..86607130 100644
--- a/ext/js/dom/selector-observer.js
+++ b/ext/js/dom/selector-observer.js
@@ -170,7 +170,7 @@ export class SelectorObserver {
 
         if (
             this._onChildrenUpdated !== null &&
-            (addedNodes.length !== 0 || addedNodes.length !== 0)
+            (removedNodes.length > 0 || addedNodes.length > 0)
         ) {
             for (let node = /** @type {?Node} */ (target); node !== null; node = node.parentNode) {
                 const observer = this._elementMap.get(node);
diff --git a/ext/js/dom/text-source-generator.js b/ext/js/dom/text-source-generator.js
index a5529779..83c7271c 100644
--- a/ext/js/dom/text-source-generator.js
+++ b/ext/js/dom/text-source-generator.js
@@ -307,8 +307,8 @@ export class TextSourceGenerator {
         // Adjust size
         const imposterRect = imposter.getBoundingClientRect();
         if (imposterRect.width !== elementRect.width || imposterRect.height !== elementRect.height) {
-            const width = parseFloat(elementStyle.width) + (elementRect.width - imposterRect.width);
-            const height = parseFloat(elementStyle.height) + (elementRect.height - imposterRect.height);
+            const width = Number.parseFloat(elementStyle.width) + (elementRect.width - imposterRect.width);
+            const height = Number.parseFloat(elementStyle.height) + (elementRect.height - imposterRect.height);
             this._setImposterStyle(imposterStyle, 'width', `${width}px`);
             this._setImposterStyle(imposterStyle, 'height', `${height}px`);
         }
@@ -614,7 +614,7 @@ export class TextSourceGenerator {
         }
         const style = window.getComputedStyle(element);
         return (
-            parseFloat(style.opacity) <= 0 ||
+            Number.parseFloat(style.opacity) <= 0 ||
             style.visibility === 'hidden' ||
             (style.backgroundImage === 'none' && this._isColorTransparent(style.backgroundColor))
         );
diff --git a/ext/js/general/object-property-accessor.js b/ext/js/general/object-property-accessor.js
index d50948d9..ac9e2a54 100644
--- a/ext/js/general/object-property-accessor.js
+++ b/ext/js/general/object-property-accessor.js
@@ -117,14 +117,14 @@ export class ObjectPropertyAccessor {
         /** @type {import('core').SerializableObject} */ (target1)[key1] = value2;
         try {
             /** @type {import('core').SerializableObject} */ (target2)[key2] = value1;
-        } catch (e) {
+        } catch (error) {
             // Revert
             try {
                 /** @type {import('core').SerializableObject} */ (target1)[key1] = value1;
-            } catch (e2) {
+            } catch (error2) {
                 // NOP
             }
-            throw e;
+            throw error;
         }
     }
 
diff --git a/ext/js/input/hotkey-handler.js b/ext/js/input/hotkey-handler.js
index 9caedcc2..6d7d3d7a 100644
--- a/ext/js/input/hotkey-handler.js
+++ b/ext/js/input/hotkey-handler.js
@@ -254,7 +254,7 @@ export class HotkeyHandler extends EventDispatcher {
      */
     _updateEventHandlers() {
         if (this._isPrepared && (this._hotkeys.size > 0 || this._hasEventListeners)) {
-            if (this._eventListeners.size !== 0) { return; }
+            if (this._eventListeners.size > 0) { return; }
             this._eventListeners.addEventListener(document, 'keydown', this._onKeyDown.bind(this), false);
         } else {
             this._eventListeners.removeAllEventListeners();
diff --git a/ext/js/language/ja/japanese.js b/ext/js/language/ja/japanese.js
index a4508040..818daa0b 100644
--- a/ext/js/language/ja/japanese.js
+++ b/ext/js/language/ja/japanese.js
@@ -92,7 +92,7 @@ const JAPANESE_RANGES = [
     [0xffe0, 0xffee] // Currency markers
 ];
 
-const SMALL_KANA_SET = new Set(Array.from('ぁぃぅぇぉゃゅょゎァィゥェォャュョヮ'));
+const SMALL_KANA_SET = new Set('ぁぃぅぇぉゃゅょゎァィゥェォャュョヮ');
 
 const HALFWIDTH_KATAKANA_MAPPING = new Map([
     ['ｦ', 'ヲヺ-'],
diff --git a/ext/js/language/text-scanner.js b/ext/js/language/text-scanner.js
index 811c7987..1cf346a9 100644
--- a/ext/js/language/text-scanner.js
+++ b/ext/js/language/text-scanner.js
@@ -1294,11 +1294,9 @@ export class TextScanner extends EventDispatcher {
     async _searchAtFromMouseMove(x, y, inputInfo) {
         if (this._pendingLookup) { return; }
 
-        if (inputInfo.passive) {
-            if (!await this._scanTimerWait()) {
-                // Aborted
-                return;
-            }
+        if (inputInfo.passive && !await this._scanTimerWait()) {
+            // Aborted
+            return;
         }
 
         await this._searchAt(x, y, inputInfo);
diff --git a/ext/js/language/translator.js b/ext/js/language/translator.js
index 007a7d1e..2ba1ce0d 100644
--- a/ext/js/language/translator.js
+++ b/ext/js/language/translator.js
@@ -491,11 +491,11 @@ export class Translator {
      * @returns {number}
      */
     _getNextSubstringLength(searchResolution, currentLength, source) {
-        if (searchResolution === 'word') {
-            return source.search(/[^\p{Letter}][\p{Letter}\p{Number}]*$/u);
-        } else {
-            return currentLength - 1;
-        }
+        return (
+            searchResolution === 'word' ?
+            source.search(/[^\p{Letter}][\p{Letter}\p{Number}]*$/u) :
+            currentLength - 1
+        );
     }
 
     /**
@@ -620,7 +620,7 @@ export class Translator {
             for (const group of groupedDictionaryEntries) {
                 this._sortTermDictionaryEntriesById(group.dictionaryEntries);
             }
-            if (ungroupedDictionaryEntriesMap.size !== 0 || secondarySearchDictionaryMap.size !== 0) {
+            if (ungroupedDictionaryEntriesMap.size > 0 || secondarySearchDictionaryMap.size > 0) {
                 await this._addSecondaryRelatedDictionaryEntries(groupedDictionaryEntries, ungroupedDictionaryEntriesMap, enabledDictionaryMap, secondarySearchDictionaryMap, tagAggregator);
             }
         }
diff --git a/ext/js/pages/action-popup-main.js b/ext/js/pages/action-popup-main.js
index b5728215..f58083a7 100644
--- a/ext/js/pages/action-popup-main.js
+++ b/ext/js/pages/action-popup-main.js
@@ -238,7 +238,7 @@ class DisplayController {
      */
     _onProfileSelectChange(event) {
         const node = /** @type {HTMLInputElement} */ (event.currentTarget);
-        const value = parseInt(node.value, 10);
+        const value = Number.parseInt(node.value, 10);
         if (typeof value === 'number' && Number.isFinite(value) && value >= 0 && value <= /** @type {import('settings').Options} */ (this._optionsFull).profiles.length) {
             this._setPrimaryProfileIndex(value);
         }
diff --git a/ext/js/pages/info-main.js b/ext/js/pages/info-main.js
index 7d7d56a5..0bc84d97 100644
--- a/ext/js/pages/info-main.js
+++ b/ext/js/pages/info-main.js
@@ -108,7 +108,7 @@ async function showDictionaryInfo(api) {
     /** @type {HTMLElement} */
     const noneElement = querySelectorNotNull(document, '#installed-dictionaries-none');
 
-    noneElement.hidden = (dictionaryInfos.length !== 0);
+    noneElement.hidden = (dictionaryInfos.length > 0);
     /** @type {HTMLElement} */
     const container = querySelectorNotNull(document, '#installed-dictionaries');
     container.textContent = '';
diff --git a/ext/js/pages/permissions-main.js b/ext/js/pages/permissions-main.js
index 3092782b..17169c12 100644
--- a/ext/js/pages/permissions-main.js
+++ b/ext/js/pages/permissions-main.js
@@ -102,6 +102,8 @@ await Application.main(async (application) => {
     /** @type {HTMLInputElement} */
     const permissionCheckbox2 = querySelectorNotNull(document, '#permission-checkbox-allow-file-url-access');
     /** @type {HTMLInputElement[]} */
+    // This collection is actually used, not sure why this eslint-disable is needed.
+    // eslint-disable-next-line sonarjs/no-unused-collection
     const permissionsCheckboxes = [permissionCheckbox1, permissionCheckbox2];
 
     const permissions = await Promise.all([
diff --git a/ext/js/pages/settings/anki-controller.js b/ext/js/pages/settings/anki-controller.js
index 3a6345ed..e161d86b 100644
--- a/ext/js/pages/settings/anki-controller.js
+++ b/ext/js/pages/settings/anki-controller.js
@@ -401,11 +401,11 @@ export class AnkiController {
         if (typeof data !== 'undefined') {
             details += `${JSON.stringify(data, null, 4)}\n\n`;
         }
-        details += `${error.stack}`.trimRight();
+        details += `${error.stack}`.trimEnd();
         /** @type {HTMLElement} */ (this._ankiErrorMessageDetailsNode).textContent = details;
 
         /** @type {HTMLElement} */ (this._ankiErrorMessageDetailsContainer).hidden = true;
-        /** @type {HTMLElement} */ (this._ankiErrorInvalidResponseInfo).hidden = (errorString.indexOf('Invalid response') < 0);
+        /** @type {HTMLElement} */ (this._ankiErrorInvalidResponseInfo).hidden = !errorString.includes('Invalid response');
         /** @type {HTMLElement} */ (this._ankiErrorMessageDetailsToggle).hidden = false;
     }
 
@@ -762,7 +762,8 @@ class AnkiCardController {
         const ELEMENT_NODE = Node.ELEMENT_NODE;
         const container = this._ankiCardFieldsContainer;
         if (container !== null) {
-            for (const node of [...container.childNodes]) {
+            const childNodesFrozen = [...container.childNodes];
+            for (const node of childNodesFrozen) {
                 if (node.nodeType === ELEMENT_NODE && node instanceof HTMLElement && node.dataset.persistent === 'true') { continue; }
                 container.removeChild(node);
             }
diff --git a/ext/js/pages/settings/audio-controller.js b/ext/js/pages/settings/audio-controller.js
index 9633c4b3..5b597d33 100644
--- a/ext/js/pages/settings/audio-controller.js
+++ b/ext/js/pages/settings/audio-controller.js
@@ -144,7 +144,7 @@ export class AudioController extends EventDispatcher {
             const text = input.value || '';
             const voiceUri = input.dataset.voice;
             const audio = this._audioSystem.createTextToSpeechAudio(text, typeof voiceUri === 'string' ? voiceUri : '');
-            audio.volume = 1.0;
+            audio.volume = 1;
             audio.play();
         } catch (e) {
             // NOP
diff --git a/ext/js/pages/settings/backup-controller.js b/ext/js/pages/settings/backup-controller.js
index 59bcaed9..2bab00e3 100644
--- a/ext/js/pages/settings/backup-controller.js
+++ b/ext/js/pages/settings/backup-controller.js
@@ -144,7 +144,7 @@ export class BackupController {
             }
         }
 
-        const data = {
+        return {
             version: this._currentVersion,
             date: this._getSettingsExportDateString(date, '-', ' ', ':', 6),
             url: chrome.runtime.getURL('/'),
@@ -154,8 +154,6 @@ export class BackupController {
             permissions,
             options: optionsFull
         };
-
-        return data;
     }
 
     /**
diff --git a/ext/js/pages/settings/collapsible-dictionary-controller.js b/ext/js/pages/settings/collapsible-dictionary-controller.js
index 5ba61e0c..62f84b96 100644
--- a/ext/js/pages/settings/collapsible-dictionary-controller.js
+++ b/ext/js/pages/settings/collapsible-dictionary-controller.js
@@ -156,9 +156,7 @@ export class CollapsibleDictionaryController {
         const versionNode = querySelectorNotNull(node, '.dictionary-version');
         versionNode.textContent = version;
 
-        /** @type {HTMLSelectElement} */
-        const select = querySelectorNotNull(node, '.definitions-collapsible');
-        return select;
+        return querySelectorNotNull(node, '.definitions-collapsible');
     }
 
     /** */
diff --git a/ext/js/pages/settings/dictionary-controller.js b/ext/js/pages/settings/dictionary-controller.js
index 1d3c1730..5020dc7c 100644
--- a/ext/js/pages/settings/dictionary-controller.js
+++ b/ext/js/pages/settings/dictionary-controller.js
@@ -558,7 +558,7 @@ export class DictionaryController {
         const {profiles} = optionsFull;
         for (let i = 0, ii = profiles.length; i < ii; ++i) {
             let modified = false;
-            const missingDictionaries = new Set([...installedDictionaries]);
+            const missingDictionaries = new Set(installedDictionaries);
             const dictionaryOptionsArray = profiles[i].options.dictionaries;
             for (let j = dictionaryOptionsArray.length - 1; j >= 0; --j) {
                 const {name} = dictionaryOptionsArray[j];
@@ -871,8 +871,8 @@ export class DictionaryController {
             const onProgress = ({processed, count, storeCount, storesProcesed}) => {
                 const percent = (
                     (count > 0 && storesProcesed > 0) ?
-                    (processed / count) * (storesProcesed / storeCount) * 100.0 :
-                    0.0
+                    (processed / count) * (storesProcesed / storeCount) * 100 :
+                    0
                 );
                 const cssString = `${percent}%`;
                 const statusString = `${percent.toFixed(0)}%`;
diff --git a/ext/js/pages/settings/dictionary-import-controller.js b/ext/js/pages/settings/dictionary-import-controller.js
index 0484001d..34e21c5d 100644
--- a/ext/js/pages/settings/dictionary-import-controller.js
+++ b/ext/js/pages/settings/dictionary-import-controller.js
@@ -172,7 +172,7 @@ export class DictionaryImportController {
                     for (const label of infoLabels) { label.textContent = labelText; }
                 }
 
-                const percent = count > 0 ? (index / count * 100.0) : 0.0;
+                const percent = count > 0 ? (index / count * 100) : 0;
                 const cssString = `${percent}%`;
                 const statusString = `${Math.floor(percent).toFixed(0)}%`;
                 for (const progressBar of progressBars) { progressBar.style.width = cssString; }
@@ -199,8 +199,8 @@ export class DictionaryImportController {
 
                 await this._importDictionary(files[i], importDetails, onProgress);
             }
-        } catch (err) {
-            this._showErrors([toError(err)]);
+        } catch (error) {
+            this._showErrors([toError(error)]);
         } finally {
             prevention.end();
             for (const progress of progressContainers) { progress.hidden = true; }
diff --git a/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js b/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js
index 61eefffa..b9d107ae 100644
--- a/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js
+++ b/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js
@@ -353,7 +353,7 @@ class ExtensionKeyboardShortcutHotkeyEntry {
      * @param {boolean} updateInput
      */
     async _tryUpdateInput(key, modifiers, updateInput) {
-        let okay = (key === null ? (modifiers.length === 0) : (modifiers.length !== 0));
+        let okay = (key === null ? (modifiers.length === 0) : (modifiers.length > 0));
         if (okay) {
             try {
                 await this._parent.updateCommand(this._name, key, modifiers);
diff --git a/ext/js/pages/settings/keyboard-shortcuts-controller.js b/ext/js/pages/settings/keyboard-shortcuts-controller.js
index 7b28a322..907cf4a1 100644
--- a/ext/js/pages/settings/keyboard-shortcuts-controller.js
+++ b/ext/js/pages/settings/keyboard-shortcuts-controller.js
@@ -183,7 +183,7 @@ export class KeyboardShortcutController {
         const listContainer = /** @type {HTMLElement} */ (this._listContainer);
         listContainer.appendChild(fragment);
         listContainer.hidden = (hotkeys.length === 0);
-        /** @type {HTMLElement} */ (this._emptyIndicator).hidden = (hotkeys.length !== 0);
+        /** @type {HTMLElement} */ (this._emptyIndicator).hidden = (hotkeys.length > 0);
     }
 
     /**
diff --git a/ext/js/pages/settings/profile-controller.js b/ext/js/pages/settings/profile-controller.js
index 5a7b5ed4..a82a4b4e 100644
--- a/ext/js/pages/settings/profile-controller.js
+++ b/ext/js/pages/settings/profile-controller.js
@@ -544,7 +544,7 @@ export class ProfileController {
      */
     _tryGetValidProfileIndex(stringValue) {
         if (typeof stringValue !== 'string') { return null; }
-        const intValue = parseInt(stringValue, 10);
+        const intValue = Number.parseInt(stringValue, 10);
         return (
             Number.isFinite(intValue) &&
             intValue >= 0 &&
@@ -573,7 +573,7 @@ export class ProfileController {
             suffix = match[5];
             if (typeof match[2] === 'string') {
                 space = match[3];
-                index = parseInt(match[4], 10) + 1;
+                index = Number.parseInt(match[4], 10) + 1;
             } else {
                 space = ' ';
                 index = 2;
diff --git a/ext/js/pages/settings/sentence-termination-characters-controller.js b/ext/js/pages/settings/sentence-termination-characters-controller.js
index c393aaa1..4ceed22b 100644
--- a/ext/js/pages/settings/sentence-termination-characters-controller.js
+++ b/ext/js/pages/settings/sentence-termination-characters-controller.js
@@ -125,8 +125,9 @@ export class SentenceTerminationCharactersController {
             entry.prepare();
         }
 
-        /** @type {HTMLElement} */ (this._listTable).hidden = (terminationCharacters.length === 0);
-        /** @type {HTMLElement} */ (this._emptyIndicator).hidden = (terminationCharacters.length !== 0);
+        const empty = terminationCharacters.length === 0;
+        /** @type {HTMLElement} */ (this._listTable).hidden = empty;
+        /** @type {HTMLElement} */ (this._emptyIndicator).hidden = !empty;
     }
 
     /**
diff --git a/ext/js/pages/settings/settings-controller.js b/ext/js/pages/settings/settings-controller.js
index 3f389271..c835f8e6 100644
--- a/ext/js/pages/settings/settings-controller.js
+++ b/ext/js/pages/settings/settings-controller.js
@@ -195,6 +195,7 @@ export class SettingsController extends EventDispatcher {
      */
     preventPageExit() {
         /** @type {import('settings-controller').PageExitPrevention} */
+        // eslint-disable-next-line sonarjs/prefer-object-literal
         const obj = {};
         obj.end = this._endPreventPageExit.bind(this, obj);
         if (this._pageExitPreventionEventListeners.size === 0) {
@@ -226,8 +227,7 @@ export class SettingsController extends EventDispatcher {
     async getDefaultOptions() {
         const optionsUtil = new OptionsUtil();
         await optionsUtil.prepare();
-        const optionsFull = optionsUtil.getDefault();
-        return optionsFull;
+        return optionsUtil.getDefault();
     }
 
     // Private
diff --git a/ext/js/pages/settings/settings-display-controller.js b/ext/js/pages/settings/settings-display-controller.js
index 0a729d96..47aa9c9c 100644
--- a/ext/js/pages/settings/settings-display-controller.js
+++ b/ext/js/pages/settings/settings-display-controller.js
@@ -290,7 +290,7 @@ export class SettingsDisplayController {
      */
     _getMoreContainer(link) {
         const v = link.dataset.parentDistance;
-        const distance = v ? parseInt(v, 10) : 1;
+        const distance = v ? Number.parseInt(v, 10) : 1;
         if (Number.isNaN(distance)) { return null; }
 
         /** @type {?Element} */
@@ -338,7 +338,7 @@ export class SettingsDisplayController {
 
         let indent = '\t';
         if (args.length > 1) {
-            const count = parseInt(args[1], 10);
+            const count = Number.parseInt(args[1], 10);
             indent = (Number.isFinite(count) && count >= 0 ? ' '.repeat(count) : args[1]);
         }
 
diff --git a/ext/js/templates/sandbox/anki-template-renderer.js b/ext/js/templates/sandbox/anki-template-renderer.js
index 2320a0b1..ad2b0042 100644
--- a/ext/js/templates/sandbox/anki-template-renderer.js
+++ b/ext/js/templates/sandbox/anki-template-renderer.js
@@ -171,11 +171,11 @@ export class AnkiTemplateRenderer {
         for (const {text, reading: reading2} of segments) {
             const safeText = this._escape(text);
             const safeReading = this._escape(reading2);
-            if (safeReading.length > 0) {
-                result += `<ruby>${safeText}<rt>${safeReading}</rt></ruby>`;
-            } else {
-                result += safeText;
-            }
+            result += (
+                safeReading.length > 0 ?
+                `<ruby>${safeText}<rt>${safeReading}</rt></ruby>` :
+                safeText
+            );
         }
 
         return this._safeString(result);