diff --git a/src/client.ts b/src/client.ts
index 45ced3946f9..220795e8b65 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -1296,9 +1296,9 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * Get the current dehydrated device, if any
      * @return {Promise} A promise of an object containing the dehydrated device
      */
-    public getDehydratedDevice(): Promise<IDehydratedDevice> {
+    public async getDehydratedDevice(): Promise<IDehydratedDevice> {
         try {
-            return this.http.authedRequest<IDehydratedDevice>(
+            return await this.http.authedRequest<IDehydratedDevice>(
                 undefined,
                 Method.Get,
                 "/dehydrated_device",
@@ -3365,7 +3365,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * data event.
      * @return {module:http-api.MatrixError} Rejects: with an error response.
      */
-    public getAccountDataFromServer<T extends {[k: string]: any}>(eventType: string): Promise<T> {
+    public async getAccountDataFromServer<T extends {[k: string]: any}>(eventType: string): Promise<T> {
         if (this.isInitialSyncComplete()) {
             const event = this.store.getAccountData(eventType);
             if (!event) {
@@ -3380,11 +3380,9 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             $type: eventType,
         });
         try {
-            return this.http.authedRequest(
-                undefined, Method.Get, path, undefined,
-            );
+            return await this.http.authedRequest(undefined, Method.Get, path);
         } catch (e) {
-            if (e.data && e.data.errcode === 'M_NOT_FOUND') {
+            if (e.data?.errcode === 'M_NOT_FOUND') {
                 return null;
             }
             throw e;
@@ -4851,7 +4849,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             }
         }
 
-        const populationResults: Record<string, Error> = {}; // {roomId: Error}
+        const populationResults: { [roomId: string]: Error } = {};
         const promises = [];
 
         const doLeave = (roomId: string) => {
@@ -5875,7 +5873,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      */
     public setRoomMutePushRule(scope: string, roomId: string, mute: boolean): Promise<void> | void {
         let promise: Promise<void>;
-        let hasDontNotifyRule;
+        let hasDontNotifyRule = false;
 
         // Get the existing room-kind push rule if any
         const roomPushRule = this.getRoomPushRule(scope, roomId);
@@ -5928,7 +5926,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
                     });
                 }).catch((err: Error) => {
                     // Update it even if the previous operation fails. This can help the
-                    // app to recover when push settings has been modifed from another client
+                    // app to recover when push settings has been modified from another client
                     this.getPushRules().then((result) => {
                         this.pushRules = result;
                         reject(err);
diff --git a/src/crypto/DeviceList.ts b/src/crypto/DeviceList.ts
index 5fdae5c245f..40c055c7b50 100644
--- a/src/crypto/DeviceList.ts
+++ b/src/crypto/DeviceList.ts
@@ -122,7 +122,7 @@ export class DeviceList extends TypedEventEmitter<EmittedEvents, CryptoEventHand
             'readonly', [IndexedDBCryptoStore.STORE_DEVICE_DATA], (txn) => {
                 this.cryptoStore.getEndToEndDeviceData(txn, (deviceData) => {
                     this.hasFetched = Boolean(deviceData && deviceData.devices);
-                    this.devices = deviceData ? deviceData.devices : {},
+                    this.devices = deviceData ? deviceData.devices : {};
                     this.crossSigningInfo = deviceData ?
                         deviceData.crossSigningInfo || {} : {};
                     this.deviceTrackingStatus = deviceData ?
@@ -190,7 +190,7 @@ export class DeviceList extends TypedEventEmitter<EmittedEvents, CryptoEventHand
 
         let savePromise = this.savePromise;
         if (savePromise === null) {
-            savePromise = new Promise((resolve, reject) => {
+            savePromise = new Promise((resolve) => {
                 this.resolveSavePromise = resolve;
             });
             this.savePromise = savePromise;
diff --git a/src/crypto/verification/SAS.ts b/src/crypto/verification/SAS.ts
index 93244464f66..a909ce7421b 100644
--- a/src/crypto/verification/SAS.ts
+++ b/src/crypto/verification/SAS.ts
@@ -271,9 +271,9 @@ export class SAS extends Base<SasEvent, EventHandlerMap> {
         do {
             try {
                 if (this.initiatedByMe) {
-                    return this.doSendVerification();
+                    return await this.doSendVerification();
                 } else {
-                    return this.doRespondVerification();
+                    return await this.doRespondVerification();
                 }
             } catch (err) {
                 if (err instanceof SwitchStartEventError) {
diff --git a/src/matrix.ts b/src/matrix.ts
index c85544e669e..e2ce5e11c9a 100644
--- a/src/matrix.ts
+++ b/src/matrix.ts
@@ -152,7 +152,7 @@ export interface ICryptoCallbacks {
 export function createClient(opts: ICreateClientOpts | string) {
     if (typeof opts === "string") {
         opts = {
-            "baseUrl": opts as string,
+            "baseUrl": opts,
         };
     }
     opts.request = opts.request || requestInstance;
diff --git a/src/models/event-timeline-set.ts b/src/models/event-timeline-set.ts
index d7396278132..aeb019112d0 100644
--- a/src/models/event-timeline-set.ts
+++ b/src/models/event-timeline-set.ts
@@ -28,7 +28,6 @@ import { EventType, RelationType } from "../@types/event";
 import { RoomState } from "./room-state";
 import { TypedEventEmitter } from "./typed-event-emitter";
 
-// var DEBUG = false;
 const DEBUG = true;
 
 let debuglog: (...args: any[]) => void;
diff --git a/src/models/room-state.ts b/src/models/room-state.ts
index d6513389948..30b87f487b9 100644
--- a/src/models/room-state.ts
+++ b/src/models/room-state.ts
@@ -26,10 +26,9 @@ import { MatrixEvent, MatrixEventEvent } from "./event";
 import { MatrixClient } from "../client";
 import { GuestAccess, HistoryVisibility, IJoinRuleEventContent, JoinRule } from "../@types/partials";
 import { TypedEventEmitter } from "./typed-event-emitter";
-import { Beacon, BeaconEvent, BeaconEventHandlerMap } from "./beacon";
+import { Beacon, BeaconEvent, BeaconEventHandlerMap, getBeaconInfoIdentifier, BeaconIdentifier } from "./beacon";
 import { TypedReEmitter } from "../ReEmitter";
 import { M_BEACON, M_BEACON_INFO } from "../@types/beacon";
-import { getBeaconInfoIdentifier, BeaconIdentifier } from "./beacon";
 
 // possible statuses for out-of-band member loading
 enum OobStatus {
diff --git a/src/models/room.ts b/src/models/room.ts
index e0769097ecd..be185255397 100644
--- a/src/models/room.ts
+++ b/src/models/room.ts
@@ -1124,14 +1124,14 @@ export class Room extends TypedEventEmitter<EmittedEvents, RoomEventHandlerMap>
      * The aliases returned by this function may not necessarily
      * still point to this room.
      * @return {array} The room's alias as an array of strings
+     * @deprecated this uses m.room.aliases events, replaced by Room::getAltAliases()
      */
     public getAliases(): string[] {
         const aliasStrings: string[] = [];
 
         const aliasEvents = this.currentState.getStateEvents(EventType.RoomAliases);
         if (aliasEvents) {
-            for (let i = 0; i < aliasEvents.length; ++i) {
-                const aliasEvent = aliasEvents[i];
+            for (const aliasEvent of aliasEvents) {
                 if (Array.isArray(aliasEvent.getContent().aliases)) {
                     const filteredAliases = aliasEvent.getContent<{ aliases: string[] }>().aliases.filter(a => {
                         if (typeof(a) !== "string") return false;
@@ -1141,7 +1141,7 @@ export class Room extends TypedEventEmitter<EmittedEvents, RoomEventHandlerMap>
                         // It's probably valid by here.
                         return true;
                     });
-                    Array.prototype.push.apply(aliasStrings, filteredAliases);
+                    aliasStrings.push(...filteredAliases);
                 }
             }
         }
@@ -1644,8 +1644,8 @@ export class Room extends TypedEventEmitter<EmittedEvents, RoomEventHandlerMap>
             eventsByThread[threadId]?.push(event);
         }
 
-        Object.entries(eventsByThread).map(([threadId, events]) => (
-            this.addThreadedEvents(threadId, events, toStartOfTimeline)
+        Object.entries(eventsByThread).map(([threadId, threadEvents]) => (
+            this.addThreadedEvents(threadId, threadEvents, toStartOfTimeline)
         ));
     }
 
@@ -2143,23 +2143,23 @@ export class Room extends TypedEventEmitter<EmittedEvents, RoomEventHandlerMap>
         const threadRoots = this.findThreadRoots(events);
         const eventsByThread: { [threadId: string]: MatrixEvent[] } = {};
 
-        for (let i = 0; i < events.length; i++) {
+        for (const event of events) {
             // TODO: We should have a filter to say "only add state event types X Y Z to the timeline".
-            this.processLiveEvent(events[i]);
+            this.processLiveEvent(event);
 
             const {
                 shouldLiveInRoom,
                 shouldLiveInThread,
                 threadId,
-            } = this.eventShouldLiveIn(events[i], events, threadRoots);
+            } = this.eventShouldLiveIn(event, events, threadRoots);
 
             if (shouldLiveInThread && !eventsByThread[threadId]) {
                 eventsByThread[threadId] = [];
             }
-            eventsByThread[threadId]?.push(events[i]);
+            eventsByThread[threadId]?.push(event);
 
             if (shouldLiveInRoom) {
-                this.addLiveEvent(events[i], duplicateStrategy, fromCache);
+                this.addLiveEvent(event, duplicateStrategy, fromCache);
             }
         }
 
diff --git a/src/store/index.ts b/src/store/index.ts
index 51d325c953f..c47bd20ad48 100644
--- a/src/store/index.ts
+++ b/src/store/index.ts
@@ -37,7 +37,7 @@ export interface ISavedSync {
 export interface IStore {
     readonly accountData: Record<string, MatrixEvent>; // type : content
 
-    /** @return {Promise<bool>} whether or not the database was newly created in this session. */
+    /** @return {Promise<boolean>} whether or not the database was newly created in this session. */
     isNewlyCreated(): Promise<boolean>;
 
     /**
diff --git a/src/store/stub.ts b/src/store/stub.ts
index 47e1188a269..1b3a8773f4e 100644
--- a/src/store/stub.ts
+++ b/src/store/stub.ts
@@ -123,7 +123,7 @@ export class StubStore implements IStore {
     /**
      * No-op.
      * @param {Room} room
-     * @param {integer} limit
+     * @param {number} limit
      * @return {Array}
      */
     public scrollback(room: Room, limit: number): MatrixEvent[] {