diff --git a/ext/bg/js/api.js b/ext/bg/js/api.js
index 766fb0ed..12257e92 100644
--- a/ext/bg/js/api.js
+++ b/ext/bg/js/api.js
@@ -45,7 +45,7 @@ async function apiOptionsSet(changedOptions, optionsContext, source) {
     function modifyOption(path, value, options) {
         let pivot = options;
         for (const key of path.slice(0, -1)) {
-            if (!pivot.hasOwnProperty(key)) {
+            if (!hasOwn(pivot, key)) {
                 return false;
             }
             pivot = pivot[key];
@@ -236,7 +236,7 @@ async function apiTemplateRender(template, data, dynamic) {
 
 async function apiCommandExec(command, params) {
     const handlers = apiCommandExec.handlers;
-    if (handlers.hasOwnProperty(command)) {
+    if (hasOwn(handlers, command)) {
         const handler = handlers[command];
         handler(params);
     }
diff --git a/ext/bg/js/audio.js b/ext/bg/js/audio.js
index cd42a158..9bbbf902 100644
--- a/ext/bg/js/audio.js
+++ b/ext/bg/js/audio.js
@@ -107,12 +107,12 @@ const audioUrlBuilders = {
     'custom': async (definition, optionsContext) => {
         const options = await apiOptionsGet(optionsContext);
         const customSourceUrl = options.audio.customSourceUrl;
-        return customSourceUrl.replace(/\{([^\}]*)\}/g, (m0, m1) => (definition.hasOwnProperty(m1) ? `${definition[m1]}` : m0));
+        return customSourceUrl.replace(/\{([^\}]*)\}/g, (m0, m1) => (hasOwn(definition, m1) ? `${definition[m1]}` : m0));
     }
 };
 
 async function audioGetUrl(definition, mode, optionsContext, download) {
-    if (audioUrlBuilders.hasOwnProperty(mode)) {
+    if (hasOwn(audioUrlBuilders, mode)) {
         const handler = audioUrlBuilders[mode];
         try {
             return await handler(definition, optionsContext, download);
@@ -171,7 +171,7 @@ async function audioInject(definition, fields, sources, optionsContext) {
 
     try {
         let audioSourceDefinition = definition;
-        if (definition.hasOwnProperty('expressions')) {
+        if (hasOwn(definition, 'expressions')) {
             audioSourceDefinition = definition.expressions[0];
         }
 
diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 45db9660..4190116b 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -73,7 +73,7 @@ class Backend {
 
     onMessage({action, params}, sender, callback) {
         const handlers = Backend.messageHandlers;
-        if (handlers.hasOwnProperty(action)) {
+        if (hasOwn(handlers, action)) {
             const handler = handlers[action];
             const promise = handler(params, sender);
             promise.then(
diff --git a/ext/bg/js/conditions-ui.js b/ext/bg/js/conditions-ui.js
index 43c6dc08..cc9db087 100644
--- a/ext/bg/js/conditions-ui.js
+++ b/ext/bg/js/conditions-ui.js
@@ -84,7 +84,7 @@ ConditionsUI.Container = class Container {
     createDefaultCondition(type) {
         let operator = '';
         let value = '';
-        if (this.conditionDescriptors.hasOwnProperty(type)) {
+        if (hasOwn(this.conditionDescriptors, type)) {
             const conditionDescriptor = this.conditionDescriptors[type];
             operator = conditionDescriptor.defaultOperator;
             ({value} = this.getOperatorDefaultValue(type, operator));
@@ -96,15 +96,15 @@ ConditionsUI.Container = class Container {
     }
 
     getOperatorDefaultValue(type, operator) {
-        if (this.conditionDescriptors.hasOwnProperty(type)) {
+        if (hasOwn(this.conditionDescriptors, type)) {
             const conditionDescriptor = this.conditionDescriptors[type];
-            if (conditionDescriptor.operators.hasOwnProperty(operator)) {
+            if (hasOwn(conditionDescriptor.operators, operator)) {
                 const operatorDescriptor = conditionDescriptor.operators[operator];
-                if (operatorDescriptor.hasOwnProperty('defaultValue')) {
+                if (hasOwn(operatorDescriptor, 'defaultValue')) {
                     return {value: operatorDescriptor.defaultValue, fromOperator: true};
                 }
             }
-            if (conditionDescriptor.hasOwnProperty('defaultValue')) {
+            if (hasOwn(conditionDescriptor, 'defaultValue')) {
                 return {value: conditionDescriptor.defaultValue, fromOperator: false};
             }
         }
@@ -219,7 +219,7 @@ ConditionsUI.Condition = class Condition {
         optionGroup.empty();
 
         const type = this.condition.type;
-        if (conditionDescriptors.hasOwnProperty(type)) {
+        if (hasOwn(conditionDescriptors, type)) {
             const conditionDescriptor = conditionDescriptors[type];
             const operators = conditionDescriptor.operators;
             for (const operatorName of Object.keys(operators)) {
@@ -240,23 +240,23 @@ ConditionsUI.Condition = class Condition {
         };
 
         const objects = [];
-        if (conditionDescriptors.hasOwnProperty(type)) {
+        if (hasOwn(conditionDescriptors, type)) {
             const conditionDescriptor = conditionDescriptors[type];
             objects.push(conditionDescriptor);
-            if (conditionDescriptor.operators.hasOwnProperty(operator)) {
+            if (hasOwn(conditionDescriptor.operators, operator)) {
                 const operatorDescriptor = conditionDescriptor.operators[operator];
                 objects.push(operatorDescriptor);
             }
         }
 
         for (const object of objects) {
-            if (object.hasOwnProperty('placeholder')) {
+            if (hasOwn(object, 'placeholder')) {
                 props.placeholder = object.placeholder;
             }
             if (object.type === 'number') {
                 props.type = 'number';
                 for (const prop of ['step', 'min', 'max']) {
-                    if (object.hasOwnProperty(prop)) {
+                    if (hasOwn(object, prop)) {
                         props[prop] = object[prop];
                     }
                 }
diff --git a/ext/bg/js/conditions.js b/ext/bg/js/conditions.js
index ed4b14f5..c0f0f301 100644
--- a/ext/bg/js/conditions.js
+++ b/ext/bg/js/conditions.js
@@ -18,14 +18,14 @@
 
 
 function conditionsValidateOptionValue(object, value) {
-    if (object.hasOwnProperty('validate') && !object.validate(value)) {
+    if (hasOwn(object, 'validate') && !object.validate(value)) {
         throw new Error('Invalid value for condition');
     }
 
-    if (object.hasOwnProperty('transform')) {
+    if (hasOwn(object, 'transform')) {
         value = object.transform(value);
 
-        if (object.hasOwnProperty('validateTransformed') && !object.validateTransformed(value)) {
+        if (hasOwn(object, 'validateTransformed') && !object.validateTransformed(value)) {
             throw new Error('Invalid value for condition');
         }
     }
@@ -34,12 +34,12 @@ function conditionsValidateOptionValue(object, value) {
 }
 
 function conditionsNormalizeOptionValue(descriptors, type, operator, optionValue) {
-    if (!descriptors.hasOwnProperty(type)) {
+    if (!hasOwn(descriptors, type)) {
         throw new Error('Invalid type');
     }
 
     const conditionDescriptor = descriptors[type];
-    if (!conditionDescriptor.operators.hasOwnProperty(operator)) {
+    if (!hasOwn(conditionDescriptor.operators, operator)) {
         throw new Error('Invalid operator');
     }
 
@@ -48,28 +48,28 @@ function conditionsNormalizeOptionValue(descriptors, type, operator, optionValue
     let transformedValue = conditionsValidateOptionValue(conditionDescriptor, optionValue);
     transformedValue = conditionsValidateOptionValue(operatorDescriptor, transformedValue);
 
-    if (operatorDescriptor.hasOwnProperty('transformReverse')) {
+    if (hasOwn(operatorDescriptor, 'transformReverse')) {
         transformedValue = operatorDescriptor.transformReverse(transformedValue);
     }
     return transformedValue;
 }
 
 function conditionsTestValueThrowing(descriptors, type, operator, optionValue, value) {
-    if (!descriptors.hasOwnProperty(type)) {
+    if (!hasOwn(descriptors, type)) {
         throw new Error('Invalid type');
     }
 
     const conditionDescriptor = descriptors[type];
-    if (!conditionDescriptor.operators.hasOwnProperty(operator)) {
+    if (!hasOwn(conditionDescriptor.operators, operator)) {
         throw new Error('Invalid operator');
     }
 
     const operatorDescriptor = conditionDescriptor.operators[operator];
-    if (operatorDescriptor.hasOwnProperty('transform')) {
-        if (operatorDescriptor.hasOwnProperty('transformCache')) {
+    if (hasOwn(operatorDescriptor, 'transform')) {
+        if (hasOwn(operatorDescriptor, 'transformCache')) {
             const key = `${optionValue}`;
             const transformCache = operatorDescriptor.transformCache;
-            if (transformCache.hasOwnProperty(key)) {
+            if (hasOwn(transformCache, key)) {
                 optionValue = transformCache[key];
             } else {
                 optionValue = operatorDescriptor.transform(optionValue);
@@ -93,23 +93,23 @@ function conditionsTestValue(descriptors, type, operator, optionValue, value) {
 
 function conditionsClearCaches(descriptors) {
     for (const type in descriptors) {
-        if (!descriptors.hasOwnProperty(type)) {
+        if (!hasOwn(descriptors, type)) {
             continue;
         }
 
         const conditionDescriptor = descriptors[type];
-        if (conditionDescriptor.hasOwnProperty('transformCache')) {
+        if (hasOwn(conditionDescriptor, 'transformCache')) {
             conditionDescriptor.transformCache = {};
         }
 
         const operatorDescriptors = conditionDescriptor.operators;
         for (const operator in operatorDescriptors) {
-            if (!operatorDescriptors.hasOwnProperty(operator)) {
+            if (!hasOwn(operatorDescriptors, operator)) {
                 continue;
             }
 
             const operatorDescriptor = operatorDescriptors[operator];
-            if (operatorDescriptor.hasOwnProperty('transformCache')) {
+            if (hasOwn(operatorDescriptor, 'transformCache')) {
                 operatorDescriptor.transformCache = {};
             }
         }
diff --git a/ext/bg/js/database.js b/ext/bg/js/database.js
index 9b560f78..c53c9f77 100644
--- a/ext/bg/js/database.js
+++ b/ext/bg/js/database.js
@@ -137,7 +137,7 @@ class Database {
         const visited = {};
         const results = [];
         const processRow = (row, index) => {
-            if (titles.includes(row.dictionary) && !visited.hasOwnProperty(row.id)) {
+            if (titles.includes(row.dictionary) && !hasOwn(visited, row.id)) {
                 visited[row.id] = true;
                 results.push(Database.createTerm(row, index));
             }
diff --git a/ext/bg/js/dictionary.js b/ext/bg/js/dictionary.js
index 9aa0af9c..affce9e9 100644
--- a/ext/bg/js/dictionary.js
+++ b/ext/bg/js/dictionary.js
@@ -81,7 +81,7 @@ function dictTermsUndupe(definitions) {
     const definitionGroups = {};
     for (const definition of definitions) {
         const definitionExisting = definitionGroups[definition.id];
-        if (!definitionGroups.hasOwnProperty(definition.id) || definition.expression.length > definitionExisting.expression.length) {
+        if (!hasOwn(definitionGroups, definition.id) || definition.expression.length > definitionExisting.expression.length) {
             definitionGroups[definition.id] = definition;
         }
     }
@@ -131,7 +131,7 @@ function dictTermsGroup(definitions, dictionaries) {
         }
 
         const keyString = key.toString();
-        if (groups.hasOwnProperty(keyString)) {
+        if (hasOwn(groups, keyString)) {
             groups[keyString].push(definition);
         } else {
             groups[keyString] = [definition];
diff --git a/ext/bg/js/mecab.js b/ext/bg/js/mecab.js
index 246f8bba..297432e2 100644
--- a/ext/bg/js/mecab.js
+++ b/ext/bg/js/mecab.js
@@ -60,7 +60,7 @@ class Mecab {
     }
 
     onNativeMessage({sequence, data}) {
-        if (this.listeners.hasOwnProperty(sequence)) {
+        if (hasOwn(this.listeners, sequence)) {
             const {callback, timer} = this.listeners[sequence];
             clearTimeout(timer);
             callback(data);
diff --git a/ext/bg/js/options.js b/ext/bg/js/options.js
index 63d88789..358a6b45 100644
--- a/ext/bg/js/options.js
+++ b/ext/bg/js/options.js
@@ -336,7 +336,7 @@ function profileOptionsSetDefaults(options) {
 
     const combine = (target, source) => {
         for (const key in source) {
-            if (!target.hasOwnProperty(key)) {
+            if (!hasOwn(target, key)) {
                 target[key] = source[key];
             }
         }
diff --git a/ext/bg/js/search.js b/ext/bg/js/search.js
index 0922d938..16cbfbbd 100644
--- a/ext/bg/js/search.js
+++ b/ext/bg/js/search.js
@@ -234,7 +234,7 @@ class DisplaySearch extends Display {
 
     onRuntimeMessage({action, params}, sender, callback) {
         const handlers = DisplaySearch.runtimeMessageHandlers;
-        if (handlers.hasOwnProperty(action)) {
+        if (hasOwn(handlers, action)) {
             const handler = handlers[action];
             const result = handler(this, params);
             callback(result);
diff --git a/ext/bg/js/settings-dictionaries.js b/ext/bg/js/settings-dictionaries.js
index ebd380ac..177379b0 100644
--- a/ext/bg/js/settings-dictionaries.js
+++ b/ext/bg/js/settings-dictionaries.js
@@ -81,7 +81,7 @@ class SettingsDictionaryListUI {
         let changed = false;
         let optionsDictionary;
         const optionsDictionaries = this.optionsDictionaries;
-        if (optionsDictionaries.hasOwnProperty(title)) {
+        if (hasOwn(optionsDictionaries, title)) {
             optionsDictionary = optionsDictionaries[title];
         } else {
             optionsDictionary = SettingsDictionaryListUI.createDictionaryOptions();
@@ -466,7 +466,7 @@ function dictionaryErrorsShow(errors) {
         for (let e of errors) {
             console.error(e);
             e = dictionaryErrorToString(e);
-            uniqueErrors[e] = uniqueErrors.hasOwnProperty(e) ? uniqueErrors[e] + 1 : 1;
+            uniqueErrors[e] = hasOwn(uniqueErrors, e) ? uniqueErrors[e] + 1 : 1;
         }
 
         for (const e in uniqueErrors) {
diff --git a/ext/bg/js/settings-popup-preview.js b/ext/bg/js/settings-popup-preview.js
index 7d641c46..49409968 100644
--- a/ext/bg/js/settings-popup-preview.js
+++ b/ext/bg/js/settings-popup-preview.js
@@ -106,7 +106,7 @@ class SettingsPopupPreview {
     onMessage(e) {
         const {action, params} = e.data;
         const handlers = SettingsPopupPreview.messageHandlers;
-        if (handlers.hasOwnProperty(action)) {
+        if (hasOwn(handlers, action)) {
             const handler = handlers[action];
             handler(this, params);
         }
diff --git a/ext/bg/js/translator.js b/ext/bg/js/translator.js
index e27cbdff..0a0ce663 100644
--- a/ext/bg/js/translator.js
+++ b/ext/bg/js/translator.js
@@ -297,7 +297,7 @@ class Translator {
         for (const deinflection of deinflections) {
             const term = deinflection.term;
             let deinflectionArray;
-            if (uniqueDeinflectionsMap.hasOwnProperty(term)) {
+            if (hasOwn(uniqueDeinflectionsMap, term)) {
                 deinflectionArray = uniqueDeinflectionsMap[term];
             } else {
                 deinflectionArray = [];
@@ -355,7 +355,7 @@ class Translator {
         const kanjiUnique = {};
         const kanjiList = [];
         for (const c of text) {
-            if (!kanjiUnique.hasOwnProperty(c)) {
+            if (!hasOwn(kanjiUnique, c)) {
                 kanjiList.push(c);
                 kanjiUnique[c] = true;
             }
@@ -417,7 +417,7 @@ class Translator {
             const expression = term.expression;
             term.frequencies = [];
 
-            if (termsUniqueMap.hasOwnProperty(expression)) {
+            if (hasOwn(termsUniqueMap, expression)) {
                 termsUniqueMap[expression].push(term);
             } else {
                 const termList = [term];
@@ -464,7 +464,7 @@ class Translator {
 
             const category = meta.category;
             const group = (
-                stats.hasOwnProperty(category) ?
+                hasOwn(stats, category) ?
                 stats[category] :
                 (stats[category] = [])
             );
@@ -484,7 +484,7 @@ class Translator {
     async getTagMetaList(names, title) {
         const tagMetaList = [];
         const cache = (
-            this.tagCache.hasOwnProperty(title) ?
+            hasOwn(this.tagCache, title) ?
             this.tagCache[title] :
             (this.tagCache[title] = {})
         );
@@ -492,7 +492,7 @@ class Translator {
         for (const name of names) {
             const base = Translator.getNameBase(name);
 
-            if (cache.hasOwnProperty(base)) {
+            if (hasOwn(cache, base)) {
                 tagMetaList.push(cache[base]);
             } else {
                 const tagMeta = await this.database.findTagForTitle(base, title);
diff --git a/ext/fg/js/float.js b/ext/fg/js/float.js
index 089c9422..ae54be00 100644
--- a/ext/fg/js/float.js
+++ b/ext/fg/js/float.js
@@ -49,7 +49,7 @@ class DisplayFloat extends Display {
     onMessage(e) {
         const {action, params} = e.data;
         const handlers = DisplayFloat.messageHandlers;
-        if (handlers.hasOwnProperty(action)) {
+        if (hasOwn(handlers, action)) {
             const handler = handlers[action];
             handler(this, params);
         }
@@ -58,7 +58,7 @@ class DisplayFloat extends Display {
     onKeyDown(e) {
         const key = Display.getKeyFromEvent(e);
         const handlers = DisplayFloat.onKeyDownHandlers;
-        if (handlers.hasOwnProperty(key)) {
+        if (hasOwn(handlers, key)) {
             const handler = handlers[key];
             if (handler(this, e)) {
                 e.preventDefault();
diff --git a/ext/fg/js/frontend-api-receiver.js b/ext/fg/js/frontend-api-receiver.js
index fbfb3ab0..bde14646 100644
--- a/ext/fg/js/frontend-api-receiver.js
+++ b/ext/fg/js/frontend-api-receiver.js
@@ -34,7 +34,7 @@ class FrontendApiReceiver {
     onMessage(port, {id, action, params, target, senderId}) {
         if (
             target !== this.source ||
-            !this.handlers.hasOwnProperty(action)
+            !hasOwn(this.handlers, action)
         ) {
             return;
         }
diff --git a/ext/fg/js/frontend-api-sender.js b/ext/fg/js/frontend-api-sender.js
index c6eeaeb2..af998a8f 100644
--- a/ext/fg/js/frontend-api-sender.js
+++ b/ext/fg/js/frontend-api-sender.js
@@ -78,7 +78,7 @@ class FrontendApiSender {
     }
 
     onAck(id) {
-        if (!this.callbacks.hasOwnProperty(id)) {
+        if (!hasOwn(this.callbacks, id)) {
             console.warn(`ID ${id} not found for ack`);
             return;
         }
@@ -95,7 +95,7 @@ class FrontendApiSender {
     }
 
     onResult(id, data) {
-        if (!this.callbacks.hasOwnProperty(id)) {
+        if (!hasOwn(this.callbacks, id)) {
             console.warn(`ID ${id} not found`);
             return;
         }
@@ -118,7 +118,7 @@ class FrontendApiSender {
     }
 
     onError(id, reason) {
-        if (!this.callbacks.hasOwnProperty(id)) { return; }
+        if (!hasOwn(this.callbacks, id)) { return; }
         const info = this.callbacks[id];
         delete this.callbacks[id];
         info.timer = null;
diff --git a/ext/fg/js/frontend.js b/ext/fg/js/frontend.js
index ee653d78..16302e82 100644
--- a/ext/fg/js/frontend.js
+++ b/ext/fg/js/frontend.js
@@ -237,7 +237,7 @@ class Frontend {
     onWindowMessage(e) {
         const action = e.data;
         const handlers = Frontend.windowMessageHandlers;
-        if (handlers.hasOwnProperty(action)) {
+        if (hasOwn(handlers, action)) {
             const handler = handlers[action];
             handler(this);
         }
@@ -245,7 +245,7 @@ class Frontend {
 
     onRuntimeMessage({action, params}, sender, callback) {
         const handlers = Frontend.runtimeMessageHandlers;
-        if (handlers.hasOwnProperty(action)) {
+        if (hasOwn(handlers, action)) {
             const handler = handlers[action];
             const result = handler(this, params);
             callback(result);
diff --git a/ext/fg/js/popup-proxy-host.js b/ext/fg/js/popup-proxy-host.js
index d8dec4df..b2f18b97 100644
--- a/ext/fg/js/popup-proxy-host.js
+++ b/ext/fg/js/popup-proxy-host.js
@@ -50,7 +50,7 @@ class PopupProxyHost {
     }
 
     createPopup(parentId, depth) {
-        const parent = (typeof parentId === 'string' && this.popups.hasOwnProperty(parentId) ? this.popups[parentId] : null);
+        const parent = (typeof parentId === 'string' && hasOwn(this.popups, parentId) ? this.popups[parentId] : null);
         const id = `${this.nextId}`;
         if (parent !== null) {
             depth = parent.depth + 1;
@@ -70,7 +70,7 @@ class PopupProxyHost {
     }
 
     getPopup(id) {
-        if (!this.popups.hasOwnProperty(id)) {
+        if (!hasOwn(this.popups, id)) {
             throw new Error('Invalid popup ID');
         }
 
diff --git a/ext/mixed/js/audio.js b/ext/mixed/js/audio.js
index 4e9d04fa..7d5ffedd 100644
--- a/ext/mixed/js/audio.js
+++ b/ext/mixed/js/audio.js
@@ -113,7 +113,7 @@ function audioGetFromUrl(url, willDownload) {
 
 async function audioGetFromSources(expression, sources, optionsContext, willDownload, cache=null) {
     const key = `${expression.expression}:${expression.reading}`;
-    if (cache !== null && cache.hasOwnProperty(expression)) {
+    if (cache !== null && hasOwn(cache, expression)) {
         return cache[key];
     }
 
diff --git a/ext/mixed/js/core.js b/ext/mixed/js/core.js
index 8a8a2368..d82b9b4b 100644
--- a/ext/mixed/js/core.js
+++ b/ext/mixed/js/core.js
@@ -94,6 +94,10 @@ function isObject(value) {
     return typeof value === 'object' && value !== null && !Array.isArray(value);
 }
 
+function hasOwn(object, property) {
+    return Object.prototype.hasOwnProperty.call(object, property);
+}
+
 // toIterable is required on Edge for cross-window origin objects.
 function toIterable(value) {
     if (typeof Symbol !== 'undefined' && typeof value[Symbol.iterator] !== 'undefined') {
diff --git a/ext/mixed/js/display.js b/ext/mixed/js/display.js
index 854418f4..ce43b22c 100644
--- a/ext/mixed/js/display.js
+++ b/ext/mixed/js/display.js
@@ -194,7 +194,7 @@ class Display {
     onKeyDown(e) {
         const key = Display.getKeyFromEvent(e);
         const handlers = Display.onKeyDownHandlers;
-        if (handlers.hasOwnProperty(key)) {
+        if (hasOwn(handlers, key)) {
             const handler = handlers[key];
             if (handler(this, e)) {
                 e.preventDefault();
@@ -216,7 +216,7 @@ class Display {
 
     onRuntimeMessage({action, params}, sender, callback) {
         const handlers = Display.runtimeMessageHandlers;
-        if (handlers.hasOwnProperty(action)) {
+        if (hasOwn(handlers, action)) {
             const handler = handlers[action];
             const result = handler(this, params);
             callback(result);