diff --git a/ext/bg/js/database.js b/ext/bg/js/database.js
index 3b2bcfcb..31573065 100644
--- a/ext/bg/js/database.js
+++ b/ext/bg/js/database.js
@@ -87,7 +87,7 @@ class Database {
         }).then(() => {
             return this.cacheTagMeta(dictionaries);
         }).then(() => {
-            for (let result of results) {
+            for (const result of results) {
                 result.tagMeta = this.tagMetaCache[result.dictionary] || {};
             }
 
@@ -115,7 +115,7 @@ class Database {
         }).then(() => {
             return this.cacheTagMeta(dictionaries);
         }).then(() => {
-            for (let result of results) {
+            for (const result of results) {
                 result.tagMeta = this.tagMetaCache[result.dictionary] || {};
             }
 
@@ -129,7 +129,7 @@ class Database {
         }
 
         const promises = [];
-        for (let dictionary of dictionaries) {
+        for (const dictionary of dictionaries) {
             if (this.tagMetaCache[dictionary]) {
                 continue;
             }
@@ -170,7 +170,7 @@ class Database {
 
                 return this.db.dictionaries.add({title, version, revision, hasTerms, hasKanji}).then(() => {
                     const rows = [];
-                    for (let tag in tagMeta || {}) {
+                    for (const tag in tagMeta || {}) {
                         const meta = tagMeta[tag];
                         const row = sanitizeTag({
                             name: tag,
@@ -190,7 +190,7 @@ class Database {
 
         const termsLoaded = (title, entries, total, current) => {
             const rows = [];
-            for (let [expression, reading, tags, rules, score, ...glossary] of entries) {
+            for (const [expression, reading, tags, rules, score, ...glossary] of entries) {
                 rows.push({
                     expression,
                     reading,
@@ -211,7 +211,7 @@ class Database {
 
         const kanjiLoaded = (title, entries, total, current)  => {
             const rows = [];
-            for (let [character, onyomi, kunyomi, tags, ...meanings] of entries) {
+            for (const [character, onyomi, kunyomi, tags, ...meanings] of entries) {
                 rows.push({
                     character,
                     onyomi,
diff --git a/ext/bg/js/deinflector.js b/ext/bg/js/deinflector.js
index 256ae1a1..6e480068 100644
--- a/ext/bg/js/deinflector.js
+++ b/ext/bg/js/deinflector.js
@@ -32,8 +32,8 @@ class Deinflection {
                 if (this.rules.length === 0) {
                     this.definitions = definitions;
                 } else {
-                    for (let rule of this.rules) {
-                        for (let definition of definitions) {
+                    for (const rule of this.rules) {
+                        for (const definition of definitions) {
                             if (definition.rules.includes(rule)) {
                                 this.definitions.push(definition);
                             }
@@ -46,11 +46,11 @@ class Deinflection {
         };
 
         const promises = [];
-        for (let reason in reasons) {
-            for (let variant of reasons[reason]) {
+        for (const reason in reasons) {
+            for (const variant of reasons[reason]) {
                 let accept = this.rules.length === 0;
                 if (!accept) {
-                    for (let rule of this.rules) {
+                    for (const rule of this.rules) {
                         if (variant.rulesIn.includes(rule)) {
                             accept = true;
                             break;
@@ -95,8 +95,8 @@ class Deinflection {
         }
 
         const results = [];
-        for (let child of this.children) {
-            for (let result of child.gather()) {
+        for (const child of this.children) {
+            for (const result of child.gather()) {
                 if (this.reason.length > 0) {
                     result.reasons.push(this.reason);
                 }
diff --git a/ext/bg/js/translator.js b/ext/bg/js/translator.js
index 82dffd91..e7c2aac2 100644
--- a/ext/bg/js/translator.js
+++ b/ext/bg/js/translator.js
@@ -54,8 +54,8 @@ class Translator {
             }
         }).then(deinflections => {
             let definitions = [];
-            for (let deinflection of deinflections) {
-                for (let definition of deinflection.definitions) {
+            for (const deinflection of deinflections) {
+                for (const definition of deinflection.definitions) {
                     const tags = definition.tags.map(tag => buildTag(tag, definition.tagMeta));
                     tags.push(buildDictTag(definition.dictionary));
                     definitions.push({
@@ -76,7 +76,7 @@ class Translator {
             definitions = sortTermDefs(definitions, dictionaries);
 
             let length = 0;
-            for (let definition of definitions) {
+            for (const definition of definitions) {
                 length = Math.max(length, definition.source.length);
             }
 
@@ -95,7 +95,7 @@ class Translator {
         const processed = {};
         const promises = [];
 
-        for (let c of text) {
+        for (const c of text) {
             if (!processed[c]) {
                 promises.push(this.database.findKanji(c, titles));
                 processed[c] = true;
@@ -104,7 +104,7 @@ class Translator {
 
         return Promise.all(promises).then(defSets => {
             const definitions = defSets.reduce((a, b) => a.concat(b), []);
-            for (let definition of definitions) {
+            for (const definition of definitions) {
                 const tags = definition.tags.map(tag => buildTag(tag, definition.tagMeta));
                 tags.push(buildDictTag(definition.dictionary));
                 definition.tags = sortTags(tags);
@@ -130,7 +130,7 @@ class Translator {
 
         return Promise.all(promises).then(results => {
             let deinflections = [];
-            for (let result of results) {
+            for (const result of results) {
                 deinflections = deinflections.concat(result);
             }
 
@@ -139,7 +139,7 @@ class Translator {
     }
 
     processKanji(definitions) {
-        for (let definition of definitions) {
+        for (const definition of definitions) {
             const tags = definition.tags.map(tag => buildTag(tag, definition.tagMeta));
             definition.tags = sortTags(tags);
         }
diff --git a/ext/bg/js/util.js b/ext/bg/js/util.js
index 24050cf3..ec562f9f 100644
--- a/ext/bg/js/util.js
+++ b/ext/bg/js/util.js
@@ -19,7 +19,7 @@
 
 function kanjiLinks(options) {
     let result = '';
-    for (let c of options.fn(this)) {
+    for (const c of options.fn(this)) {
         if (isKanji(c)) {
             result += `<a href="#" class="kanji-link">${c}</a>`;
         } else {
@@ -41,7 +41,7 @@ function isKanji(c) {
 
 function enabledDicts(options) {
     const dictionaries = {};
-    for (let title in options.dictionaries) {
+    for (const title in options.dictionaries) {
         const dictionary = options.dictionaries[title];
         if (dictionary.enabled) {
             dictionaries[title] = dictionary;
@@ -104,7 +104,7 @@ function sortTermDefs(definitions, dictionaries=null) {
 
 function undupeTermDefs(definitions) {
     const definitionGroups = {};
-    for (let definition of definitions) {
+    for (const definition of definitions) {
         const definitionExisting = definitionGroups[definition.id];
         if (!definitionGroups.hasOwnProperty(definition.id) || definition.expression.length > definitionExisting.expression.length) {
             definitionGroups[definition.id] = definition;
@@ -112,7 +112,7 @@ function undupeTermDefs(definitions) {
     }
 
     const definitionsUnique = [];
-    for (let key in definitionGroups) {
+    for (const key in definitionGroups) {
         definitionsUnique.push(definitionGroups[key]);
     }
 
@@ -121,7 +121,7 @@ function undupeTermDefs(definitions) {
 
 function groupTermDefs(definitions, dictionaries) {
     const groups = {};
-    for (let definition of definitions) {
+    for (const definition of definitions) {
         const key = [definition.source, definition.expression].concat(definition.reasons);
         if (definition.reading) {
             key.push(definition.reading);
@@ -136,7 +136,7 @@ function groupTermDefs(definitions, dictionaries) {
     }
 
     const results = [];
-    for (let key in groups) {
+    for (const key in groups) {
         const groupDefs = groups[key];
         const firstDef = groupDefs[0];
         sortTermDefs(groupDefs, dictionaries);
@@ -160,7 +160,7 @@ function buildDictTag(name) {
 function buildTag(name, meta) {
     const tag = {name};
     const symbol = name.split(':')[0];
-    for (let prop in meta[symbol] || {}) {
+    for (const prop in meta[symbol] || {}) {
         tag[prop] = meta[symbol][prop];
     }
 
@@ -217,7 +217,7 @@ function formatField(field, definition, mode, options) {
         'url'
     ];
 
-    for (let marker of markers) {
+    for (const marker of markers) {
         const data = {
             marker,
             definition,
@@ -304,7 +304,7 @@ function importJsonDb(indexUrl, indexLoaded, termsLoaded, kanjiLoaded) {
         }
 
         let chain = Promise.resolve();
-        for (let loader of loaders) {
+        for (const loader of loaders) {
             chain = chain.then(loader);
         }