diff --git a/ext/bg/js/handlebars.js b/ext/bg/js/handlebars.js
index d6307e1d..8f43cf9a 100644
--- a/ext/bg/js/handlebars.js
+++ b/ext/bg/js/handlebars.js
@@ -89,7 +89,7 @@ function handlebarsRegexReplace(...args) {
     let value = args[args.length - 1].fn(this);
     if (args.length >= 3) {
         try {
-            let flags = args.length > 3 ? args[2] : 'g';
+            const flags = args.length > 3 ? args[2] : 'g';
             const regex = new RegExp(args[0], flags);
             value = value.replace(regex, args[1]);
         } catch (e) {
diff --git a/ext/bg/js/search-query-parser.js b/ext/bg/js/search-query-parser.js
index 1a43347c..2bf24ce3 100644
--- a/ext/bg/js/search-query-parser.js
+++ b/ext/bg/js/search-query-parser.js
@@ -134,7 +134,7 @@ class QueryParser {
             });
         }
         if (this.search.options.parsing.enableMecabParser) {
-            let mecabResults = await apiTextParseMecab(text, this.search.getOptionsContext());
+            const mecabResults = await apiTextParseMecab(text, this.search.getOptionsContext());
             for (const mecabDictName in mecabResults) {
                 results.push({
                     name: `MeCab: ${mecabDictName}`,
diff --git a/ext/bg/js/search.js b/ext/bg/js/search.js
index 552b7a59..e5cdf272 100644
--- a/ext/bg/js/search.js
+++ b/ext/bg/js/search.js
@@ -356,7 +356,7 @@ class DisplaySearch extends Display {
     }
 
     static getSearchQueryFromLocation(url) {
-        let match = /^[^?#]*\?(?:[^&#]*&)?query=([^&#]*)/.exec(url);
+        const match = /^[^?#]*\?(?:[^&#]*&)?query=([^&#]*)/.exec(url);
         return match !== null ? decodeURIComponent(match[1]) : null;
     }
 }
diff --git a/ext/fg/js/frontend.js b/ext/fg/js/frontend.js
index 16302e82..8297f54d 100644
--- a/ext/fg/js/frontend.js
+++ b/ext/fg/js/frontend.js
@@ -447,8 +447,8 @@ class Frontend {
     }
 
     getIndexOfTouch(touchList, identifier) {
-        for (let i in touchList) {
-            let t = touchList[i];
+        for (const i in touchList) {
+            const t = touchList[i];
             if (t.identifier === identifier) {
                 return i;
             }
diff --git a/ext/fg/js/source.js b/ext/fg/js/source.js
index 886093d7..e6b991c4 100644
--- a/ext/fg/js/source.js
+++ b/ext/fg/js/source.js
@@ -361,7 +361,7 @@ class TextSourceElement {
 
         let consumed = 0;
         let content = '';
-        for (let currentChar of this.content || '') {
+        for (const currentChar of this.content || '') {
             if (consumed >= length) {
                 break;
             } else if (!currentChar.match(IGNORE_TEXT_PATTERN)) {