diff --git a/app/assets/javascripts/admin/addon/mixins/setting-object.js b/app/assets/javascripts/admin/addon/mixins/setting-object.js
index 63567ebde67..1830cc89847 100644
--- a/app/assets/javascripts/admin/addon/mixins/setting-object.js
+++ b/app/assets/javascripts/admin/addon/mixins/setting-object.js
@@ -63,7 +63,7 @@ export default Mixin.create({
 
   @discourseComputed("valid_values")
   allowsNone(validValues) {
-    if (validValues && validValues.indexOf("") >= 0) {
+    if (validValues?.includes("")) {
       return "admin.settings.none";
     }
   },
diff --git a/app/assets/javascripts/discourse-common/addon/lib/icon-library.js b/app/assets/javascripts/discourse-common/addon/lib/icon-library.js
index 62d280e6124..86650a1c701 100644
--- a/app/assets/javascripts/discourse-common/addon/lib/icon-library.js
+++ b/app/assets/javascripts/discourse-common/addon/lib/icon-library.js
@@ -121,7 +121,7 @@ export function setIconList(iconList) {
 }
 
 export function isExistingIconId(id) {
-  return _iconList && _iconList.indexOf(id) >= 0;
+  return _iconList.includes(id);
 }
 
 function warnIfMissing(id) {
diff --git a/app/assets/javascripts/discourse/app/components/color-picker-choice.js b/app/assets/javascripts/discourse/app/components/color-picker-choice.js
index a5773f73212..0dabe8c810a 100644
--- a/app/assets/javascripts/discourse/app/components/color-picker-choice.js
+++ b/app/assets/javascripts/discourse/app/components/color-picker-choice.js
@@ -10,7 +10,7 @@ export default Component.extend({
 
   @discourseComputed("color", "usedColors")
   isUsed(color, usedColors) {
-    return (usedColors || []).indexOf(color.toUpperCase()) >= 0;
+    return (usedColors || []).includes(color.toUpperCase());
   },
 
   @discourseComputed("isUsed")
diff --git a/app/assets/javascripts/discourse/app/lib/uploads.js b/app/assets/javascripts/discourse/app/lib/uploads.js
index eb316d3f883..d019cfd84ef 100644
--- a/app/assets/javascripts/discourse/app/lib/uploads.js
+++ b/app/assets/javascripts/discourse/app/lib/uploads.js
@@ -198,8 +198,8 @@ function authorizedImagesExtensions(staff, siteSettings) {
 
 export function authorizesAllExtensions(staff, siteSettings) {
   return (
-    siteSettings.authorized_extensions.indexOf("*") >= 0 ||
-    (siteSettings.authorized_extensions_for_staff.indexOf("*") >= 0 && staff)
+    siteSettings.authorized_extensions.includes("*") ||
+    (siteSettings.authorized_extensions_for_staff.includes("*") && staff)
   );
 }
 
diff --git a/app/assets/javascripts/discourse/app/models/topic-list.js b/app/assets/javascripts/discourse/app/models/topic-list.js
index b019da21827..c108f8b41e9 100644
--- a/app/assets/javascripts/discourse/app/models/topic-list.js
+++ b/app/assets/javascripts/discourse/app/models/topic-list.js
@@ -120,7 +120,7 @@ const TopicList = RestModel.extend({
   loadBefore(topic_ids, storeInSession) {
     // refresh dupes
     this.topics.removeObjects(
-      this.topics.filter((topic) => topic_ids.indexOf(topic.id) >= 0)
+      this.topics.filter((topic) => topic_ids.includes(topic.id))
     );
 
     const url = `${getURL("/")}${this.filter}.json?topic_ids=${topic_ids.join(
diff --git a/app/assets/javascripts/discourse/app/models/topic.js b/app/assets/javascripts/discourse/app/models/topic.js
index 200436454d8..53b4af4e209 100644
--- a/app/assets/javascripts/discourse/app/models/topic.js
+++ b/app/assets/javascripts/discourse/app/models/topic.js
@@ -61,9 +61,7 @@ const Topic = RestModel.extend({
   @discourseComputed("posters.[]")
   lastPoster(posters) {
     if (posters && posters.length > 0) {
-      const latest = posters.filter(
-        (p) => p.extras && p.extras.indexOf("latest") >= 0
-      )[0];
+      const latest = posters.filter((p) => p.extras?.includes("latest"))[0];
       return latest || posters.firstObject;
     }
   },
diff --git a/app/assets/javascripts/discourse/app/models/user-action.js b/app/assets/javascripts/discourse/app/models/user-action.js
index a1a567720ec..15ff9e0a3f7 100644
--- a/app/assets/javascripts/discourse/app/models/user-action.js
+++ b/app/assets/javascripts/discourse/app/models/user-action.js
@@ -31,7 +31,7 @@ const UserAction = RestModel.extend({
 
   @discourseComputed("action_type")
   descriptionKey(action) {
-    if (action === null || UserAction.TO_SHOW.indexOf(action) >= 0) {
+    if (action === null || UserAction.TO_SHOW.includes(action)) {
       if (this.isPM) {
         return this.sameUser ? "sent_by_you" : "sent_by_user";
       } else {
@@ -180,7 +180,7 @@ UserAction.reopenClass({
       const found = uniq[key];
       if (found === void 0) {
         let current;
-        if (UserAction.TO_COLLAPSE.indexOf(item.action_type) >= 0) {
+        if (UserAction.TO_COLLAPSE.includes(item.action_type)) {
           current = UserAction.create(item);
           item.switchToActing();
           current.addChild(item);
@@ -191,7 +191,7 @@ UserAction.reopenClass({
         collapsed[pos] = current;
         pos += 1;
       } else {
-        if (UserAction.TO_COLLAPSE.indexOf(item.action_type) >= 0) {
+        if (UserAction.TO_COLLAPSE.includes(item.action_type)) {
           item.switchToActing();
           collapsed[found].addChild(item);
         } else {
diff --git a/app/assets/javascripts/discourse/app/routes/discovery-categories.js b/app/assets/javascripts/discourse/app/routes/discovery-categories.js
index f689c27e87d..d7b1970d3fb 100644
--- a/app/assets/javascripts/discourse/app/routes/discovery-categories.js
+++ b/app/assets/javascripts/discourse/app/routes/discovery-categories.js
@@ -47,7 +47,7 @@ const DiscoveryCategoriesRoute = DiscourseRoute.extend(OpenComposer, {
     return function (topic_ids, storeInSession) {
       // refresh dupes
       this.topics.removeObjects(
-        this.topics.filter((topic) => topic_ids.indexOf(topic.id) >= 0)
+        this.topics.filter((topic) => topic_ids.includes(topic.id))
       );
 
       const url = `${getURL("/")}latest.json?topic_ids=${topic_ids.join(",")}`;
diff --git a/app/assets/javascripts/discourse/app/widgets/post-cooked.js b/app/assets/javascripts/discourse/app/widgets/post-cooked.js
index 5ccbde2f92a..9cceb2cc51f 100644
--- a/app/assets/javascripts/discourse/app/widgets/post-cooked.js
+++ b/app/assets/javascripts/discourse/app/widgets/post-cooked.js
@@ -129,7 +129,7 @@ export default class PostCooked {
 
         // this might be an attachment
         if (lc.internal && /^\/uploads\//.test(lc.url)) {
-          valid = href.indexOf(lc.url) >= 0;
+          valid = href.includes(lc.url);
         }
 
         // Match server-side behaviour for internal links with query params
diff --git a/app/assets/javascripts/select-kit/addon/components/mini-tag-chooser/selected-collection.js b/app/assets/javascripts/select-kit/addon/components/mini-tag-chooser/selected-collection.js
index 9ccbe516280..fc563c4698d 100644
--- a/app/assets/javascripts/select-kit/addon/components/mini-tag-chooser/selected-collection.js
+++ b/app/assets/javascripts/select-kit/addon/components/mini-tag-chooser/selected-collection.js
@@ -17,7 +17,7 @@ export default Component.extend({
 
     let tags = this.selectedTags;
     if (tags.length >= 20 && this.selectKit.filter) {
-      tags = tags.filter((t) => t.indexOf(this.selectKit.filter) >= 0);
+      tags = tags.filter((t) => t.includes(this.selectKit.filter));
     } else if (tags.length >= 20) {
       tags = tags.slice(0, 20);
     }