diff --git a/framework/core/js/src/admin/AdminApplication.ts b/framework/core/js/src/admin/AdminApplication.ts
index 62fa121b5..301662cdf 100644
--- a/framework/core/js/src/admin/AdminApplication.ts
+++ b/framework/core/js/src/admin/AdminApplication.ts
@@ -5,6 +5,7 @@ import Application, { ApplicationData } from '../common/Application';
 import Navigation from '../common/components/Navigation';
 import AdminNav from './components/AdminNav';
 import ExtensionData from './utils/ExtensionData';
+import IHistory from '../common/IHistory';
 
 export type Extension = {
   id: string;
@@ -47,13 +48,16 @@ export default class AdminApplication extends Application {
     language: 10,
   };
 
-  history = {
+  history: IHistory = {
     canGoBack: () => true,
-    getPrevious: () => {},
+    getCurrent: () => null,
+    getPrevious: () => null,
+    push: () => {},
     backUrl: () => this.forum.attribute<string>('baseUrl'),
     back: function () {
       window.location.assign(this.backUrl());
     },
+    home: () => {},
   };
 
   /**
diff --git a/framework/core/js/src/common/Application.tsx b/framework/core/js/src/common/Application.tsx
index 36af01500..4a58c8de6 100644
--- a/framework/core/js/src/common/Application.tsx
+++ b/framework/core/js/src/common/Application.tsx
@@ -34,6 +34,7 @@ import type Component from './Component';
 import type { ComponentAttrs } from './Component';
 import Model, { SavedModelData } from './Model';
 import fireApplicationError from './helpers/fireApplicationError';
+import IHistory from './IHistory';
 
 export type FlarumScreens = 'phone' | 'tablet' | 'desktop' | 'desktop-hd';
 
@@ -228,6 +229,9 @@ export default class Application {
    */
   drawer!: Drawer;
 
+  history: IHistory | null = null;
+  pane: any = null;
+
   data!: ApplicationData;
 
   private _title: string = '';
diff --git a/framework/core/js/src/common/Component.ts b/framework/core/js/src/common/Component.ts
index 36c12a83e..fdf244443 100644
--- a/framework/core/js/src/common/Component.ts
+++ b/framework/core/js/src/common/Component.ts
@@ -156,5 +156,5 @@ export default abstract class Component<Attrs extends ComponentAttrs = Component
    *
    * This can be used to assign default values for missing, optional attrs.
    */
-  static initAttrs<T>(attrs: T): void {}
+  static initAttrs(attrs: unknown): void {}
 }
diff --git a/framework/core/js/src/common/IHistory.ts b/framework/core/js/src/common/IHistory.ts
new file mode 100644
index 000000000..936ab643b
--- /dev/null
+++ b/framework/core/js/src/common/IHistory.ts
@@ -0,0 +1,15 @@
+export interface HistoryEntry {
+  name: string;
+  title: string;
+  url: string;
+}
+
+export default interface IHistory {
+  canGoBack(): boolean;
+  getCurrent(): HistoryEntry | null;
+  getPrevious(): HistoryEntry | null;
+  push(name: string, title: string, url: string): void;
+  back(): void;
+  backUrl(): string;
+  home(): void;
+}
diff --git a/framework/core/js/src/common/components/Badge.js b/framework/core/js/src/common/components/Badge.tsx
similarity index 81%
rename from framework/core/js/src/common/components/Badge.js
rename to framework/core/js/src/common/components/Badge.tsx
index 39f63e16b..4261e8d95 100644
--- a/framework/core/js/src/common/components/Badge.js
+++ b/framework/core/js/src/common/components/Badge.tsx
@@ -1,8 +1,15 @@
 import Tooltip from './Tooltip';
-import Component from '../Component';
+import Component, { ComponentAttrs } from '../Component';
 import icon from '../helpers/icon';
 import classList from '../utils/classList';
 
+export interface IBadgeAttrs extends ComponentAttrs {
+  icon: string;
+  type?: string;
+  label?: string;
+  color?: string;
+}
+
 /**
  * The `Badge` component represents a user/discussion badge, indicating some
  * status (e.g. a discussion is stickied, a user is an admin).
@@ -16,7 +23,7 @@ import classList from '../utils/classList';
  *
  * All other attrs will be assigned as attributes on the badge element.
  */
-export default class Badge extends Component {
+export default class Badge<CustomAttrs extends IBadgeAttrs = IBadgeAttrs> extends Component<CustomAttrs> {
   view() {
     const { type, icon: iconName, label, color, style = {}, ...attrs } = this.attrs;
 
diff --git a/framework/core/js/src/common/components/Checkbox.js b/framework/core/js/src/common/components/Checkbox.tsx
similarity index 74%
rename from framework/core/js/src/common/components/Checkbox.js
rename to framework/core/js/src/common/components/Checkbox.tsx
index bc7ed5db1..975dc17c3 100644
--- a/framework/core/js/src/common/components/Checkbox.js
+++ b/framework/core/js/src/common/components/Checkbox.tsx
@@ -1,8 +1,16 @@
-import Component from '../Component';
+import Component, { ComponentAttrs } from '../Component';
 import LoadingIndicator from './LoadingIndicator';
 import icon from '../helpers/icon';
 import classList from '../utils/classList';
 import withAttr from '../utils/withAttr';
+import type Mithril from 'mithril';
+
+export interface ICheckboxAttrs extends ComponentAttrs {
+  state?: boolean;
+  loading?: boolean;
+  disabled?: boolean;
+  onchange: (checked: boolean, component: Checkbox<this>) => void;
+}
 
 /**
  * The `Checkbox` component defines a checkbox input.
@@ -16,12 +24,8 @@ import withAttr from '../utils/withAttr';
  * - `onchange` A callback to run when the checkbox is checked/unchecked.
  * - `children` A text label to display next to the checkbox.
  */
-export default class Checkbox extends Component {
-  view(vnode) {
-    // Sometimes, false is stored in the DB as '0'. This is a temporary
-    // conversion layer until a more robust settings encoding is introduced
-    if (this.attrs.state === '0') this.attrs.state = false;
-
+export default class Checkbox<CustomAttrs extends ICheckboxAttrs = ICheckboxAttrs> extends Component<CustomAttrs> {
+  view(vnode: Mithril.Vnode<CustomAttrs, this>) {
     const className = classList([
       'Checkbox',
       this.attrs.state ? 'on' : 'off',
@@ -43,21 +47,15 @@ export default class Checkbox extends Component {
 
   /**
    * Get the template for the checkbox's display (tick/cross icon).
-   *
-   * @return {import('mithril').Children}
-   * @protected
    */
-  getDisplay() {
+  protected getDisplay(): Mithril.Children {
     return this.attrs.loading ? <LoadingIndicator display="unset" size="small" /> : icon(this.attrs.state ? 'fas fa-check' : 'fas fa-times');
   }
 
   /**
    * Run a callback when the state of the checkbox is changed.
-   *
-   * @param {boolean} checked
-   * @protected
    */
-  onchange(checked) {
+  protected onchange(checked: boolean): void {
     if (this.attrs.onchange) this.attrs.onchange(checked, this);
   }
 }
diff --git a/framework/core/js/src/common/components/GroupBadge.js b/framework/core/js/src/common/components/GroupBadge.js
deleted file mode 100644
index 5479f7db0..000000000
--- a/framework/core/js/src/common/components/GroupBadge.js
+++ /dev/null
@@ -1,16 +0,0 @@
-import Badge from './Badge';
-
-export default class GroupBadge extends Badge {
-  static initAttrs(attrs) {
-    super.initAttrs(attrs);
-
-    if (attrs.group) {
-      attrs.icon = attrs.group.icon();
-      attrs.color = attrs.group.color();
-      attrs.label = typeof attrs.label === 'undefined' ? attrs.group.nameSingular() : attrs.label;
-      attrs.type = 'group--' + attrs.group.id();
-
-      delete attrs.group;
-    }
-  }
-}
diff --git a/framework/core/js/src/common/components/GroupBadge.tsx b/framework/core/js/src/common/components/GroupBadge.tsx
new file mode 100644
index 000000000..4910a004f
--- /dev/null
+++ b/framework/core/js/src/common/components/GroupBadge.tsx
@@ -0,0 +1,21 @@
+import Badge, { IBadgeAttrs } from './Badge';
+import Group from '../models/Group';
+
+export interface IGroupAttrs extends IBadgeAttrs {
+  group?: Group;
+}
+
+export default class GroupBadge<CustomAttrs extends IGroupAttrs = IGroupAttrs> extends Badge<CustomAttrs> {
+  static initAttrs(attrs: IGroupAttrs): void {
+    super.initAttrs(attrs);
+
+    if (attrs.group) {
+      attrs.icon = attrs.group.icon() || '';
+      attrs.color = attrs.group.color() || '';
+      attrs.label = typeof attrs.label === 'undefined' ? attrs.group.nameSingular() : attrs.label;
+      attrs.type = 'group--' + attrs.group.id();
+
+      delete attrs.group;
+    }
+  }
+}
diff --git a/framework/core/js/src/common/components/Navigation.js b/framework/core/js/src/common/components/Navigation.tsx
similarity index 80%
rename from framework/core/js/src/common/components/Navigation.js
rename to framework/core/js/src/common/components/Navigation.tsx
index 157d07538..de2cb3e2a 100644
--- a/framework/core/js/src/common/components/Navigation.js
+++ b/framework/core/js/src/common/components/Navigation.tsx
@@ -2,6 +2,7 @@ import app from '../../common/app';
 import Component from '../Component';
 import Button from './Button';
 import LinkButton from './LinkButton';
+import type Mithril from 'mithril';
 
 /**
  * The `Navigation` component displays a set of navigation buttons. Typically
@@ -28,41 +29,35 @@ export default class Navigation extends Component {
         onmouseenter={pane && pane.show.bind(pane)}
         onmouseleave={pane && pane.onmouseleave.bind(pane)}
       >
-        {history.canGoBack() ? [this.getBackButton(), this.getPaneButton()] : this.getDrawerButton()}
+        {history?.canGoBack() ? [this.getBackButton(), this.getPaneButton()] : this.getDrawerButton()}
       </div>
     );
   }
 
   /**
    * Get the back button.
-   *
-   * @return {import('mithril').Children}
-   * @protected
    */
-  getBackButton() {
+  protected getBackButton(): Mithril.Children {
     const { history } = app;
-    const previous = history.getPrevious() || {};
+    const previous = history?.getPrevious();
 
     return LinkButton.component({
       className: 'Button Navigation-back Button--icon',
-      href: history.backUrl(),
+      href: history?.backUrl(),
       icon: 'fas fa-chevron-left',
-      'aria-label': previous.title,
-      onclick: (e) => {
+      'aria-label': previous?.title,
+      onclick: (e: MouseEvent) => {
         if (e.shiftKey || e.ctrlKey || e.metaKey || e.which === 2) return;
         e.preventDefault();
-        history.back();
+        history?.back();
       },
     });
   }
 
   /**
    * Get the pane pinned toggle button.
-   *
-   * @return {import('mithril').Children}
-   * @protected
    */
-  getPaneButton() {
+  protected getPaneButton(): Mithril.Children {
     const { pane } = app;
 
     if (!pane || !pane.active) return '';
@@ -76,11 +71,8 @@ export default class Navigation extends Component {
 
   /**
    * Get the drawer toggle button.
-   *
-   * @return {import('mithril').Children}
-   * @protected
    */
-  getDrawerButton() {
+  protected getDrawerButton(): Mithril.Children {
     if (!this.attrs.drawer) return '';
 
     const { drawer } = app;
@@ -88,7 +80,7 @@ export default class Navigation extends Component {
 
     return Button.component({
       className: 'Button Button--icon Navigation-drawer' + (user && user.newNotificationCount() ? ' new' : ''),
-      onclick: (e) => {
+      onclick: (e: MouseEvent) => {
         e.stopPropagation();
         drawer.show();
       },
diff --git a/framework/core/js/src/common/components/Switch.js b/framework/core/js/src/common/components/Switch.tsx
similarity index 77%
rename from framework/core/js/src/common/components/Switch.js
rename to framework/core/js/src/common/components/Switch.tsx
index 531c4347a..faf928f66 100644
--- a/framework/core/js/src/common/components/Switch.js
+++ b/framework/core/js/src/common/components/Switch.tsx
@@ -1,11 +1,11 @@
-import Checkbox from './Checkbox';
+import Checkbox, { ICheckboxAttrs } from './Checkbox';
 
 /**
  * The `Switch` component is a `Checkbox`, but with a switch display instead of
  * a tick/cross one.
  */
 export default class Switch extends Checkbox {
-  static initAttrs(attrs) {
+  static initAttrs(attrs: ICheckboxAttrs) {
     super.initAttrs(attrs);
 
     attrs.className = (attrs.className || '') + ' Checkbox--switch';
diff --git a/framework/core/js/src/forum/utils/History.ts b/framework/core/js/src/forum/utils/History.ts
index faa8e8da4..778533386 100644
--- a/framework/core/js/src/forum/utils/History.ts
+++ b/framework/core/js/src/forum/utils/History.ts
@@ -1,10 +1,5 @@
 import setRouteWithForcedRefresh from '../../common/utils/setRouteWithForcedRefresh';
-
-export interface HistoryEntry {
-  name: string;
-  title: string;
-  url: string;
-}
+import IHistory, { HistoryEntry } from '../../common/IHistory';
 
 /**
  * The `History` class keeps track and manages a stack of routes that the user
@@ -17,7 +12,7 @@ export interface HistoryEntry {
  * popping the history stack will still take them back to the discussion list
  * rather than the previous discussion.
  */
-export default class History {
+export default class History implements IHistory {
   /**
    * The stack of routes that have been navigated to.
    */