diff --git a/.eslintignore b/.eslintignore
index 4f01beef6df6..cdc0de02b21f 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -30,7 +30,6 @@ webpack.config.ts
 
 # Temporarily ignored during TSLint transition
 # JIRA: DESKTOP-304
-ts/*.ts
 ts/components/*.ts
 ts/components/*.tsx
 ts/components/conversation/**
diff --git a/ts/ConversationController.ts b/ts/ConversationController.ts
index cd27b717f196..c48c3cfb7cf0 100644
--- a/ts/ConversationController.ts
+++ b/ts/ConversationController.ts
@@ -1,5 +1,3 @@
-const MAX_MESSAGE_BODY_LENGTH = 64 * 1024;
-
 import { debounce, reduce, uniq, without } from 'lodash';
 import dataInterface from './sql/Client';
 import {
@@ -9,6 +7,8 @@ import {
 } from './model-types.d';
 import { SendOptionsType } from './textsecure/SendMessage';
 
+const MAX_MESSAGE_BODY_LENGTH = 64 * 1024;
+
 const {
   getAllConversations,
   getAllGroupsInvolvingId,
@@ -22,7 +22,7 @@ const {
 // We have to run this in background.js, after all backbone models and collections on
 //   Whisper.* have been created. Once those are in typescript we can use more reasonable
 //   require statements for referencing these things, giving us more flexibility here.
-export function start() {
+export function start(): void {
   const conversations = new window.Whisper.ConversationCollection();
 
   // This class is entirely designed to keep the app title, badge and tray icon updated.
@@ -70,7 +70,9 @@ export function start() {
 
 export class ConversationController {
   _initialFetchComplete: boolean | undefined;
+
   _initialPromise: Promise<void> = Promise.resolve();
+
   _conversations: ConversationModelCollectionType;
 
   constructor(conversations?: ConversationModelCollectionType) {
@@ -91,14 +93,18 @@ export class ConversationController {
     // This function takes null just fine. Backbone typings are too restrictive.
     return this._conversations.get(id as string);
   }
-  dangerouslyCreateAndAdd(attributes: Partial<ConversationModelType>) {
+
+  dangerouslyCreateAndAdd(
+    attributes: Partial<ConversationModelType>
+  ): ConversationModelType {
     return this._conversations.add(attributes);
   }
+
   getOrCreate(
     identifier: string,
     type: ConversationTypeType,
     additionalInitialProps = {}
-  ) {
+  ): ConversationModelType {
     if (typeof identifier !== 'string') {
       throw new TypeError("'id' must be a string");
     }
@@ -186,24 +192,24 @@ export class ConversationController {
 
     return conversation;
   }
+
   async getOrCreateAndWait(
     id: string,
     type: ConversationTypeType,
     additionalInitialProps = {}
-  ) {
-    return this._initialPromise.then(async () => {
-      const conversation = this.getOrCreate(id, type, additionalInitialProps);
+  ): Promise<ConversationModelType> {
+    await this._initialPromise;
+    const conversation = this.getOrCreate(id, type, additionalInitialProps);
 
-      if (conversation) {
-        return conversation.initialPromise.then(() => conversation);
-      }
+    if (conversation) {
+      await conversation.initialPromise;
+      return conversation;
+    }
 
-      return Promise.reject(
-        new Error('getOrCreateAndWait: did not get conversation')
-      );
-    });
+    throw new Error('getOrCreateAndWait: did not get conversation');
   }
-  getConversationId(address: string) {
+
+  getConversationId(address: string): string | null {
     if (!address) {
       return null;
     }
@@ -217,11 +223,13 @@ export class ConversationController {
 
     return null;
   }
+
   getOurConversationId(): string | undefined {
     const e164 = window.textsecure.storage.user.getNumber();
     const uuid = window.textsecure.storage.user.getUuid();
     return this.ensureContactIds({ e164, uuid, highTrust: true });
   }
+
   /**
    * Given a UUID and/or an E164, resolves to a string representing the local
    * database id of the given contact. In high trust mode, it may create new contacts,
@@ -272,7 +280,8 @@ export class ConversationController {
       return newConvo.get('id');
 
       // 2. Handle match on only E164
-    } else if (convoE164 && !convoUuid) {
+    }
+    if (convoE164 && !convoUuid) {
       const haveUuid = Boolean(normalizedUuid);
       window.log.info(
         `ensureContactIds: e164-only match found (have UUID: ${haveUuid})`
@@ -315,7 +324,8 @@ export class ConversationController {
       return newConvo.get('id');
 
       // 3. Handle match on only UUID
-    } else if (!convoE164 && convoUuid) {
+    }
+    if (!convoE164 && convoUuid) {
       window.log.info(
         `ensureContactIds: UUID-only match found (have e164: ${Boolean(e164)})`
       );
@@ -363,6 +373,8 @@ export class ConversationController {
       // Conflict: If e164 match has no UUID, we merge. We prefer the UUID match.
       // Note: no await here, we want to keep this function synchronous
       convoUuid.updateE164(e164);
+      // `then` is used to trigger async updates, not affecting return value
+      // eslint-disable-next-line more/no-then
       this.combineContacts(convoUuid, convoE164)
         .then(() => {
           // If the old conversation was currently displayed, we load the new one
@@ -381,7 +393,8 @@ export class ConversationController {
 
     return convoUuid.get('id');
   }
-  async checkForConflicts() {
+
+  async checkForConflicts(): Promise<void> {
     window.log.info('checkForConflicts: starting...');
     const byUuid = Object.create(null);
     const byE164 = Object.create(null);
@@ -465,10 +478,11 @@ export class ConversationController {
 
     window.log.info('checkForConflicts: complete!');
   }
+
   async combineContacts(
     current: ConversationModelType,
     obsolete: ConversationModelType
-  ) {
+  ): Promise<void> {
     const obsoleteId = obsolete.get('id');
     const currentId = current.get('id');
     window.log.warn('combineContacts: Combining two conversations', {
@@ -541,6 +555,7 @@ export class ConversationController {
       current: currentId,
     });
   }
+
   /**
    * Given a groupId and optional additional initialization properties,
    * ensures the existence of a group conversation and returns a string
@@ -549,16 +564,17 @@ export class ConversationController {
   ensureGroup(groupId: string, additionalInitProps = {}): string {
     return this.getOrCreate(groupId, 'group', additionalInitProps).get('id');
   }
+
   /**
    * Given certain metadata about a message (an identifier of who wrote the
    * message and the sent_at timestamp of the message) returns the
    * conversation the message belongs to OR null if a conversation isn't
    * found.
    */
-  async getConversationForTargetMessage(
+  static async getConversationForTargetMessage(
     targetFromId: string,
     targetTimestamp: number
-  ) {
+  ): Promise<boolean | ConversationModelType | null | undefined> {
     const messages = await getMessagesBySentAt(targetTimestamp, {
       MessageCollection: window.Whisper.MessageCollection,
     });
@@ -579,11 +595,12 @@ export class ConversationController {
 
     return null;
   }
-  prepareForSend(
+
+  prepareForSend<T>(
     id: string,
-    options?: any
+    options?: unknown
   ): {
-    wrap: (promise: Promise<any>) => Promise<void>;
+    wrap: (promise: Promise<T>) => Promise<T>;
     sendOptions: SendOptionsType | undefined;
   } {
     // id is any valid conversation identifier
@@ -593,10 +610,11 @@ export class ConversationController {
       : undefined;
     const wrap = conversation
       ? conversation.wrapSend.bind(conversation)
-      : async (promise: Promise<any>) => promise;
+      : async (promise: Promise<T>) => promise;
 
     return { wrap, sendOptions };
   }
+
   async getAllGroupsInvolvingId(
     conversationId: string
   ): Promise<Array<ConversationModelType>> {
@@ -605,18 +623,22 @@ export class ConversationController {
     });
     return groups.map(group => this._conversations.add(group));
   }
-  async loadPromise() {
+
+  async loadPromise(): Promise<void> {
     return this._initialPromise;
   }
-  reset() {
+
+  reset(): void {
     this._initialPromise = Promise.resolve();
     this._initialFetchComplete = false;
     this._conversations.reset([]);
   }
-  isFetchComplete() {
+
+  isFetchComplete(): boolean | undefined {
     return this._initialFetchComplete;
   }
-  async load() {
+
+  async load(): Promise<void> {
     window.log.info('ConversationController: starting initial fetch');
 
     if (this._conversations.length) {
diff --git a/ts/Crypto.ts b/ts/Crypto.ts
index ce4578ad8f50..968a19849b51 100644
--- a/ts/Crypto.ts
+++ b/ts/Crypto.ts
@@ -1,55 +1,47 @@
 import pProps from 'p-props';
 
-// Yep, we're doing some bitwise stuff in an encryption-related file
-// tslint:disable no-bitwise
-
-// We want some extra variables to make the decrption algorithm easier to understand
-// tslint:disable no-unnecessary-local-variable
-
-// Seems that tslint doesn't understand that crypto.subtle.importKey does return a Promise
-// tslint:disable await-promise
-
 export function typedArrayToArrayBuffer(typedArray: Uint8Array): ArrayBuffer {
   const { buffer, byteOffset, byteLength } = typedArray;
 
-  // tslint:disable-next-line no-unnecessary-type-assertion
   return buffer.slice(byteOffset, byteLength + byteOffset) as typeof typedArray;
 }
 
-export function arrayBufferToBase64(arrayBuffer: ArrayBuffer) {
+export function arrayBufferToBase64(arrayBuffer: ArrayBuffer): string {
   return window.dcodeIO.ByteBuffer.wrap(arrayBuffer).toString('base64');
 }
 
-export function arrayBufferToHex(arrayBuffer: ArrayBuffer) {
+export function arrayBufferToHex(arrayBuffer: ArrayBuffer): string {
   return window.dcodeIO.ByteBuffer.wrap(arrayBuffer).toString('hex');
 }
 
-export function base64ToArrayBuffer(base64string: string) {
+export function base64ToArrayBuffer(base64string: string): ArrayBuffer {
   return window.dcodeIO.ByteBuffer.wrap(base64string, 'base64').toArrayBuffer();
 }
 
-export function hexToArrayBuffer(hexString: string) {
+export function hexToArrayBuffer(hexString: string): ArrayBuffer {
   return window.dcodeIO.ByteBuffer.wrap(hexString, 'hex').toArrayBuffer();
 }
 
-export function fromEncodedBinaryToArrayBuffer(key: string) {
+export function fromEncodedBinaryToArrayBuffer(key: string): ArrayBuffer {
   return window.dcodeIO.ByteBuffer.wrap(key, 'binary').toArrayBuffer();
 }
 
-export function bytesFromString(string: string) {
+export function bytesFromString(string: string): ArrayBuffer {
   return window.dcodeIO.ByteBuffer.wrap(string, 'utf8').toArrayBuffer();
 }
-export function stringFromBytes(buffer: ArrayBuffer) {
+export function stringFromBytes(buffer: ArrayBuffer): string {
   return window.dcodeIO.ByteBuffer.wrap(buffer).toString('utf8');
 }
-export function hexFromBytes(buffer: ArrayBuffer) {
+export function hexFromBytes(buffer: ArrayBuffer): string {
   return window.dcodeIO.ByteBuffer.wrap(buffer).toString('hex');
 }
-export function bytesFromHexString(string: string) {
+export function bytesFromHexString(string: string): ArrayBuffer {
   return window.dcodeIO.ByteBuffer.wrap(string, 'hex').toArrayBuffer();
 }
 
-export async function deriveStickerPackKey(packKey: ArrayBuffer) {
+export async function deriveStickerPackKey(
+  packKey: ArrayBuffer
+): Promise<ArrayBuffer> {
   const salt = getZeroes(32);
   const info = bytesFromString('Sticker Pack');
 
@@ -72,7 +64,7 @@ export async function computeHash(data: ArrayBuffer): Promise<string> {
 export async function encryptDeviceName(
   deviceName: string,
   identityPublic: ArrayBuffer
-) {
+): Promise<Record<string, ArrayBuffer>> {
   const plaintext = bytesFromString(deviceName);
   const ephemeralKeyPair = await window.libsignal.KeyHelper.generateIdentityKeyPair();
   const masterSecret = await window.libsignal.Curve.async.calculateAgreement(
@@ -107,7 +99,7 @@ export async function decryptDeviceName(
     ciphertext: ArrayBuffer;
   },
   identityPrivate: ArrayBuffer
-) {
+): Promise<string> {
   const masterSecret = await window.libsignal.Curve.async.calculateAgreement(
     ephemeralPublic,
     identityPrivate
@@ -130,7 +122,7 @@ export async function decryptDeviceName(
 }
 
 // Path structure: 'fa/facdf99c22945b1c9393345599a276f4b36ad7ccdc8c2467f5441b742c2d11fa'
-export function getAttachmentLabel(path: string) {
+export function getAttachmentLabel(path: string): ArrayBuffer {
   const filename = path.slice(3);
 
   return base64ToArrayBuffer(filename);
@@ -141,7 +133,7 @@ export async function encryptAttachment(
   staticPublicKey: ArrayBuffer,
   path: string,
   plaintext: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const uniqueId = getAttachmentLabel(path);
 
   return encryptFile(staticPublicKey, uniqueId, plaintext);
@@ -151,7 +143,7 @@ export async function decryptAttachment(
   staticPrivateKey: ArrayBuffer,
   path: string,
   data: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const uniqueId = getAttachmentLabel(path);
 
   return decryptFile(staticPrivateKey, uniqueId, data);
@@ -161,7 +153,7 @@ export async function encryptFile(
   staticPublicKey: ArrayBuffer,
   uniqueId: ArrayBuffer,
   plaintext: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const ephemeralKeyPair = await window.libsignal.KeyHelper.generateIdentityKeyPair();
   const agreement = await window.libsignal.Curve.async.calculateAgreement(
     staticPublicKey,
@@ -178,7 +170,7 @@ export async function decryptFile(
   staticPrivateKey: ArrayBuffer,
   uniqueId: ArrayBuffer,
   data: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const ephemeralPublicKey = getFirstBytes(data, PUB_KEY_LENGTH);
   const ciphertext = getBytes(data, PUB_KEY_LENGTH, data.byteLength);
   const agreement = await window.libsignal.Curve.async.calculateAgreement(
@@ -194,18 +186,20 @@ export async function decryptFile(
 export async function deriveStorageManifestKey(
   storageServiceKey: ArrayBuffer,
   version: number
-) {
+): Promise<ArrayBuffer> {
   return hmacSha256(storageServiceKey, bytesFromString(`Manifest_${version}`));
 }
 
 export async function deriveStorageItemKey(
   storageServiceKey: ArrayBuffer,
   itemID: string
-) {
+): Promise<ArrayBuffer> {
   return hmacSha256(storageServiceKey, bytesFromString(`Item_${itemID}`));
 }
 
-export async function deriveAccessKey(profileKey: ArrayBuffer) {
+export async function deriveAccessKey(
+  profileKey: ArrayBuffer
+): Promise<ArrayBuffer> {
   const iv = getZeroes(12);
   const plaintext = getZeroes(16);
   const accessKey = await encryptAesGcm(profileKey, iv, plaintext);
@@ -213,7 +207,9 @@ export async function deriveAccessKey(profileKey: ArrayBuffer) {
   return getFirstBytes(accessKey, 16);
 }
 
-export async function getAccessKeyVerifier(accessKey: ArrayBuffer) {
+export async function getAccessKeyVerifier(
+  accessKey: ArrayBuffer
+): Promise<ArrayBuffer> {
   const plaintext = getZeroes(32);
 
   return hmacSha256(accessKey, plaintext);
@@ -222,7 +218,7 @@ export async function getAccessKeyVerifier(accessKey: ArrayBuffer) {
 export async function verifyAccessKey(
   accessKey: ArrayBuffer,
   theirVerifier: ArrayBuffer
-) {
+): Promise<boolean> {
   const ourVerifier = await getAccessKeyVerifier(accessKey);
 
   if (constantTimeEqual(ourVerifier, theirVerifier)) {
@@ -239,14 +235,14 @@ const NONCE_LENGTH = 16;
 export async function encryptSymmetric(
   key: ArrayBuffer,
   plaintext: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const iv = getZeroes(IV_LENGTH);
   const nonce = getRandomBytes(NONCE_LENGTH);
 
   const cipherKey = await hmacSha256(key, nonce);
   const macKey = await hmacSha256(key, cipherKey);
 
-  const cipherText = await _encrypt_aes256_CBC_PKCSPadding(
+  const cipherText = await _encryptAes256CbcPkcsPadding(
     cipherKey,
     iv,
     plaintext
@@ -256,7 +252,10 @@ export async function encryptSymmetric(
   return concatenateBytes(nonce, cipherText, mac);
 }
 
-export async function decryptSymmetric(key: ArrayBuffer, data: ArrayBuffer) {
+export async function decryptSymmetric(
+  key: ArrayBuffer,
+  data: ArrayBuffer
+): Promise<ArrayBuffer> {
   const iv = getZeroes(IV_LENGTH);
 
   const nonce = getFirstBytes(data, NONCE_LENGTH);
@@ -280,10 +279,13 @@ export async function decryptSymmetric(key: ArrayBuffer, data: ArrayBuffer) {
     );
   }
 
-  return _decrypt_aes256_CBC_PKCSPadding(cipherKey, iv, cipherText);
+  return _decryptAes256CbcPkcsPadding(cipherKey, iv, cipherText);
 }
 
-export function constantTimeEqual(left: ArrayBuffer, right: ArrayBuffer) {
+export function constantTimeEqual(
+  left: ArrayBuffer,
+  right: ArrayBuffer
+): boolean {
   if (left.byteLength !== right.byteLength) {
     return false;
   }
@@ -301,8 +303,11 @@ export function constantTimeEqual(left: ArrayBuffer, right: ArrayBuffer) {
 
 // Encryption
 
-export async function hmacSha256(key: ArrayBuffer, plaintext: ArrayBuffer) {
-  const algorithm = {
+export async function hmacSha256(
+  key: ArrayBuffer,
+  plaintext: ArrayBuffer
+): Promise<ArrayBuffer> {
+  const algorithm: HmacImportParams = {
     name: 'HMAC',
     hash: 'SHA-256',
   };
@@ -311,7 +316,7 @@ export async function hmacSha256(key: ArrayBuffer, plaintext: ArrayBuffer) {
   const cryptoKey = await window.crypto.subtle.importKey(
     'raw',
     key,
-    algorithm as any,
+    algorithm,
     extractable,
     ['sign']
   );
@@ -319,11 +324,11 @@ export async function hmacSha256(key: ArrayBuffer, plaintext: ArrayBuffer) {
   return window.crypto.subtle.sign(algorithm, cryptoKey, plaintext);
 }
 
-export async function _encrypt_aes256_CBC_PKCSPadding(
+export async function _encryptAes256CbcPkcsPadding(
   key: ArrayBuffer,
   iv: ArrayBuffer,
   plaintext: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const algorithm = {
     name: 'AES-CBC',
     iv,
@@ -333,6 +338,10 @@ export async function _encrypt_aes256_CBC_PKCSPadding(
   const cryptoKey = await window.crypto.subtle.importKey(
     'raw',
     key,
+    // `algorithm` appears to be an instance of AesCbcParams,
+    // which is not in the param's types, so we need to pass as `any`.
+    // TODO: just pass the string "AES-CBC", per the docs?
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     algorithm as any,
     extractable,
     ['encrypt']
@@ -341,11 +350,11 @@ export async function _encrypt_aes256_CBC_PKCSPadding(
   return window.crypto.subtle.encrypt(algorithm, cryptoKey, plaintext);
 }
 
-export async function _decrypt_aes256_CBC_PKCSPadding(
+export async function _decryptAes256CbcPkcsPadding(
   key: ArrayBuffer,
   iv: ArrayBuffer,
   plaintext: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const algorithm = {
     name: 'AES-CBC',
     iv,
@@ -355,6 +364,10 @@ export async function _decrypt_aes256_CBC_PKCSPadding(
   const cryptoKey = await window.crypto.subtle.importKey(
     'raw',
     key,
+    // `algorithm` appears to be an instance of AesCbcParams,
+    // which is not in the param's types, so we need to pass as `any`.
+    // TODO: just pass the string "AES-CBC", per the docs?
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     algorithm as any,
     extractable,
     ['decrypt']
@@ -367,7 +380,7 @@ export async function encryptAesCtr(
   key: ArrayBuffer,
   plaintext: ArrayBuffer,
   counter: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const extractable = false;
   const algorithm = {
     name: 'AES-CTR',
@@ -378,6 +391,10 @@ export async function encryptAesCtr(
   const cryptoKey = await crypto.subtle.importKey(
     'raw',
     key,
+    // `algorithm` appears to be an instance of AesCtrParams,
+    // which is not in the param's types, so we need to pass as `any`.
+    // TODO: just pass the string "AES-CTR", per the docs?
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     algorithm as any,
     extractable,
     ['encrypt']
@@ -396,7 +413,7 @@ export async function decryptAesCtr(
   key: ArrayBuffer,
   ciphertext: ArrayBuffer,
   counter: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const extractable = false;
   const algorithm = {
     name: 'AES-CTR',
@@ -407,6 +424,10 @@ export async function decryptAesCtr(
   const cryptoKey = await crypto.subtle.importKey(
     'raw',
     key,
+    // `algorithm` appears to be an instance of AesCtrParams,
+    // which is not in the param's types, so we need to pass as `any`.
+    // TODO: just pass the string "AES-CTR", per the docs?
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     algorithm as any,
     extractable,
     ['decrypt']
@@ -425,7 +446,7 @@ export async function encryptAesGcm(
   iv: ArrayBuffer,
   plaintext: ArrayBuffer,
   additionalData?: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const algorithm = {
     name: 'AES-GCM',
     iv,
@@ -437,6 +458,10 @@ export async function encryptAesGcm(
   const cryptoKey = await crypto.subtle.importKey(
     'raw',
     key,
+    // `algorithm` appears to be an instance of AesGcmParams,
+    // which is not in the param's types, so we need to pass as `any`.
+    // TODO: just pass the string "AES-GCM", per the docs?
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     algorithm as any,
     extractable,
     ['encrypt']
@@ -450,7 +475,7 @@ export async function decryptAesGcm(
   iv: ArrayBuffer,
   ciphertext: ArrayBuffer,
   additionalData?: ArrayBuffer
-) {
+): Promise<ArrayBuffer> {
   const algorithm = {
     name: 'AES-GCM',
     iv,
@@ -462,6 +487,10 @@ export async function decryptAesGcm(
   const cryptoKey = await crypto.subtle.importKey(
     'raw',
     key,
+    // `algorithm` appears to be an instance of AesGcmParams,
+    // which is not in the param's types, so we need to pass as `any`.
+    // TODO: just pass the string "AES-GCM", per the docs?
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     algorithm as any,
     extractable,
     ['decrypt']
@@ -472,13 +501,13 @@ export async function decryptAesGcm(
 
 // Hashing
 
-export async function sha256(data: ArrayBuffer) {
+export async function sha256(data: ArrayBuffer): Promise<ArrayBuffer> {
   return crypto.subtle.digest('SHA-256', data);
 }
 
 // Utility
 
-export function getRandomBytes(n: number) {
+export function getRandomBytes(n: number): ArrayBuffer {
   const bytes = new Uint8Array(n);
   window.crypto.getRandomValues(bytes);
 
@@ -496,7 +525,7 @@ export function getRandomValue(low: number, high: number): number {
   return (bytes[0] % mod) + low;
 }
 
-export function getZeroes(n: number) {
+export function getZeroes(n: number): ArrayBuffer {
   const result = new Uint8Array(n);
 
   const value = 0;
@@ -508,6 +537,7 @@ export function getZeroes(n: number) {
 }
 
 export function highBitsToInt(byte: number): number {
+  // eslint-disable-next-line no-bitwise
   return (byte & 0xff) >> 4;
 }
 
@@ -515,10 +545,11 @@ export function intsToByteHighAndLow(
   highValue: number,
   lowValue: number
 ): number {
+  // eslint-disable-next-line no-bitwise
   return ((highValue << 4) | lowValue) & 0xff;
 }
 
-export function trimBytes(buffer: ArrayBuffer, length: number) {
+export function trimBytes(buffer: ArrayBuffer, length: number): ArrayBuffer {
   return getFirstBytes(buffer, length);
 }
 
@@ -526,14 +557,16 @@ export function getViewOfArrayBuffer(
   buffer: ArrayBuffer,
   start: number,
   finish: number
-) {
+): ArrayBuffer | SharedArrayBuffer {
   const source = new Uint8Array(buffer);
   const result = source.slice(start, finish);
 
   return result.buffer;
 }
 
-export function concatenateBytes(...elements: Array<ArrayBuffer | Uint8Array>) {
+export function concatenateBytes(
+  ...elements: Array<ArrayBuffer | Uint8Array>
+): ArrayBuffer {
   const length = elements.reduce(
     (total, element) => total + element.byteLength,
     0
@@ -585,7 +618,7 @@ export function splitBytes(
   return results;
 }
 
-export function getFirstBytes(data: ArrayBuffer, n: number) {
+export function getFirstBytes(data: ArrayBuffer, n: number): ArrayBuffer {
   const source = new Uint8Array(data);
 
   return typedArrayToArrayBuffer(source.subarray(0, n));
@@ -595,7 +628,7 @@ export function getBytes(
   data: ArrayBuffer | Uint8Array,
   start: number,
   n: number
-) {
+): ArrayBuffer {
   const source = new Uint8Array(data);
 
   return typedArrayToArrayBuffer(source.subarray(start, start + n));
@@ -614,7 +647,7 @@ export async function encryptCdsDiscoveryRequest(
     [key: string]: { clientKey: ArrayBuffer; requestId: ArrayBuffer };
   },
   phoneNumbers: ReadonlyArray<string>
-) {
+): Promise<Record<string, unknown>> {
   const nonce = getRandomBytes(32);
   const numbersArray = new window.dcodeIO.ByteBuffer(
     phoneNumbers.length * 8,
@@ -669,7 +702,7 @@ export async function encryptCdsDiscoveryRequest(
   };
 }
 
-export function splitUuids(arrayBuffer: ArrayBuffer) {
+export function splitUuids(arrayBuffer: ArrayBuffer): Array<string | null> {
   const uuids = [];
   for (let i = 0; i < arrayBuffer.byteLength; i += 16) {
     const bytes = getBytes(arrayBuffer, i, 16);
diff --git a/ts/OS.ts b/ts/OS.ts
index e6a215f23349..d9c1d4cd868d 100644
--- a/ts/OS.ts
+++ b/ts/OS.ts
@@ -2,9 +2,9 @@ import is from '@sindresorhus/is';
 import os from 'os';
 import semver from 'semver';
 
-export const isMacOS = () => process.platform === 'darwin';
-export const isLinux = () => process.platform === 'linux';
-export const isWindows = (minVersion?: string) => {
+export const isMacOS = (): boolean => process.platform === 'darwin';
+export const isLinux = (): boolean => process.platform === 'linux';
+export const isWindows = (minVersion?: string): boolean => {
   const osRelease = os.release();
 
   if (process.platform !== 'win32') {
diff --git a/ts/RemoteConfig.ts b/ts/RemoteConfig.ts
index 12fa4597f2ce..595a602bb7b5 100644
--- a/ts/RemoteConfig.ts
+++ b/ts/RemoteConfig.ts
@@ -34,12 +34,15 @@ function getServer(): WebAPIType {
 let config: ConfigMapType = {};
 const listeners: ConfigListenersMapType = {};
 
-export async function initRemoteConfig() {
+export async function initRemoteConfig(): Promise<void> {
   config = window.storage.get('remoteConfig') || {};
   await maybeRefreshRemoteConfig();
 }
 
-export function onChange(key: ConfigKeyType, fn: ConfigListenerType) {
+export function onChange(
+  key: ConfigKeyType,
+  fn: ConfigListenerType
+): () => void {
   const keyListeners: Array<ConfigListenerType> = get(listeners, key, []);
   keyListeners.push(fn);
   listeners[key] = keyListeners;
@@ -49,7 +52,7 @@ export function onChange(key: ConfigKeyType, fn: ConfigListenerType) {
   };
 }
 
-export const refreshRemoteConfig = async () => {
+export const refreshRemoteConfig = async (): Promise<void> => {
   const now = Date.now();
   const server = getServer();
   const newConfig = await server.getConfig();
@@ -61,7 +64,8 @@ export const refreshRemoteConfig = async () => {
   config = newConfig.reduce((acc, { name, enabled, value }) => {
     const previouslyEnabled: boolean = get(oldConfig, [name, 'enabled'], false);
     const previousValue: unknown = get(oldConfig, [name, 'value'], undefined);
-    // If a flag was previously not enabled and is now enabled, record the time it was enabled
+    // If a flag was previously not enabled and is now enabled,
+    // record the time it was enabled
     const enabledAt: number | undefined =
       previouslyEnabled && enabled ? now : get(oldConfig, [name, 'enabledAt']);
 
diff --git a/ts/groupChange.ts b/ts/groupChange.ts
index 606169e87e9f..e009360c6821 100644
--- a/ts/groupChange.ts
+++ b/ts/groupChange.ts
@@ -26,7 +26,7 @@ export type RenderOptionsType = {
 export function renderChange(
   change: GroupV2ChangeType,
   options: RenderOptionsType
-) {
+): Array<FullJSXType> {
   const { details, from } = change;
 
   return details.map((detail: GroupV2ChangeDetailType) =>
@@ -37,7 +37,6 @@ export function renderChange(
   );
 }
 
-// tslint:disable-next-line cyclomatic-complexity max-func-body-length
 export function renderChangeDetail(
   detail: GroupV2ChangeDetailType,
   options: RenderOptionsType
@@ -59,108 +58,103 @@ export function renderChangeDetail(
     if (newTitle) {
       if (fromYou) {
         return renderString('GroupV2--title--change--you', i18n, [newTitle]);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--title--change--other', i18n, {
           memberName: renderContact(from),
           newTitle,
         });
-      } else {
-        return renderString('GroupV2--title--change--unknown', i18n, [
-          newTitle,
-        ]);
-      }
-    } else {
-      if (fromYou) {
-        return renderString('GroupV2--title--remove--you', i18n);
-      } else if (from) {
-        return renderString('GroupV2--title--remove--other', i18n, [
-          renderContact(from),
-        ]);
-      } else {
-        return renderString('GroupV2--title--remove--unknown', i18n);
       }
+      return renderString('GroupV2--title--change--unknown', i18n, [newTitle]);
     }
-  } else if (detail.type === 'avatar') {
+    if (fromYou) {
+      return renderString('GroupV2--title--remove--you', i18n);
+    }
+    if (from) {
+      return renderString('GroupV2--title--remove--other', i18n, [
+        renderContact(from),
+      ]);
+    }
+    return renderString('GroupV2--title--remove--unknown', i18n);
+  }
+  if (detail.type === 'avatar') {
     if (detail.removed) {
       if (fromYou) {
         return renderString('GroupV2--avatar--remove--you', i18n);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--avatar--remove--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString('GroupV2--avatar--remove--unknown', i18n);
-      }
-    } else {
-      if (fromYou) {
-        return renderString('GroupV2--avatar--change--you', i18n);
-      } else if (from) {
-        return renderString('GroupV2--avatar--change--other', i18n, [
-          renderContact(from),
-        ]);
-      } else {
-        return renderString('GroupV2--avatar--change--unknown', i18n);
       }
+      return renderString('GroupV2--avatar--remove--unknown', i18n);
     }
-  } else if (detail.type === 'access-attributes') {
+    if (fromYou) {
+      return renderString('GroupV2--avatar--change--you', i18n);
+    }
+    if (from) {
+      return renderString('GroupV2--avatar--change--other', i18n, [
+        renderContact(from),
+      ]);
+    }
+    return renderString('GroupV2--avatar--change--unknown', i18n);
+  }
+  if (detail.type === 'access-attributes') {
     const { newPrivilege } = detail;
 
     if (newPrivilege === AccessControlEnum.ADMINISTRATOR) {
       if (fromYou) {
         return renderString('GroupV2--access-attributes--admins--you', i18n);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--access-attributes--admins--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString(
-          'GroupV2--access-attributes--admins--unknown',
-          i18n
-        );
       }
-    } else if (newPrivilege === AccessControlEnum.MEMBER) {
+      return renderString('GroupV2--access-attributes--admins--unknown', i18n);
+    }
+    if (newPrivilege === AccessControlEnum.MEMBER) {
       if (fromYou) {
         return renderString('GroupV2--access-attributes--all--you', i18n);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--access-attributes--all--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString('GroupV2--access-attributes--all--unknown', i18n);
       }
-    } else {
-      throw new Error(
-        `access-attributes change type, privilege ${newPrivilege} is unknown`
-      );
+      return renderString('GroupV2--access-attributes--all--unknown', i18n);
     }
+    throw new Error(
+      `access-attributes change type, privilege ${newPrivilege} is unknown`
+    );
   } else if (detail.type === 'access-members') {
     const { newPrivilege } = detail;
 
     if (newPrivilege === AccessControlEnum.ADMINISTRATOR) {
       if (fromYou) {
         return renderString('GroupV2--access-members--admins--you', i18n);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--access-members--admins--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString('GroupV2--access-members--admins--unknown', i18n);
       }
-    } else if (newPrivilege === AccessControlEnum.MEMBER) {
+      return renderString('GroupV2--access-members--admins--unknown', i18n);
+    }
+    if (newPrivilege === AccessControlEnum.MEMBER) {
       if (fromYou) {
         return renderString('GroupV2--access-members--all--you', i18n);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--access-members--all--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString('GroupV2--access-members--all--unknown', i18n);
       }
-    } else {
-      throw new Error(
-        `access-members change type, privilege ${newPrivilege} is unknown`
-      );
+      return renderString('GroupV2--access-members--all--unknown', i18n);
     }
+    throw new Error(
+      `access-members change type, privilege ${newPrivilege} is unknown`
+    );
   } else if (detail.type === 'member-add') {
     const { conversationId } = detail;
     const weAreJoiner = conversationId === ourConversationId;
@@ -168,29 +162,28 @@ export function renderChangeDetail(
     if (weAreJoiner) {
       if (fromYou) {
         return renderString('GroupV2--member-add--you--you', i18n);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--member-add--you--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString('GroupV2--member-add--you--unknown', i18n);
-      }
-    } else {
-      if (fromYou) {
-        return renderString('GroupV2--member-add--other--you', i18n, [
-          renderContact(conversationId),
-        ]);
-      } else if (from) {
-        return renderString('GroupV2--member-add--other--other', i18n, {
-          adderName: renderContact(from),
-          addeeName: renderContact(conversationId),
-        });
-      } else {
-        return renderString('GroupV2--member-add--other--unknown', i18n, [
-          renderContact(conversationId),
-        ]);
       }
+      return renderString('GroupV2--member-add--you--unknown', i18n);
     }
+    if (fromYou) {
+      return renderString('GroupV2--member-add--other--you', i18n, [
+        renderContact(conversationId),
+      ]);
+    }
+    if (from) {
+      return renderString('GroupV2--member-add--other--other', i18n, {
+        adderName: renderContact(from),
+        addeeName: renderContact(conversationId),
+      });
+    }
+    return renderString('GroupV2--member-add--other--unknown', i18n, [
+      renderContact(conversationId),
+    ]);
   } else if (detail.type === 'member-add-from-invite') {
     const { conversationId, inviter } = detail;
     const weAreJoiner = conversationId === ourConversationId;
@@ -200,16 +193,16 @@ export function renderChangeDetail(
       return renderString('GroupV2--member-add--from-invite--you', i18n, [
         renderContact(inviter),
       ]);
-    } else if (weAreInviter) {
+    }
+    if (weAreInviter) {
       return renderString('GroupV2--member-add--from-invite--from-you', i18n, [
         renderContact(conversationId),
       ]);
-    } else {
-      return renderString('GroupV2--member-add--from-invite--other', i18n, {
-        inviteeName: renderContact(conversationId),
-        inviterName: renderContact(inviter),
-      });
     }
+    return renderString('GroupV2--member-add--from-invite--other', i18n, {
+      inviteeName: renderContact(conversationId),
+      inviterName: renderContact(inviter),
+    });
   } else if (detail.type === 'member-remove') {
     const { conversationId } = detail;
     const weAreLeaver = conversationId === ourConversationId;
@@ -217,33 +210,34 @@ export function renderChangeDetail(
     if (weAreLeaver) {
       if (fromYou) {
         return renderString('GroupV2--member-remove--you--you', i18n);
-      } else if (from) {
+      }
+      if (from) {
         return renderString('GroupV2--member-remove--you--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString('GroupV2--member-remove--you--unknown', i18n);
-      }
-    } else {
-      if (fromYou) {
-        return renderString('GroupV2--member-remove--other--you', i18n, [
-          renderContact(conversationId),
-        ]);
-      } else if (from && from === conversationId) {
-        return renderString('GroupV2--member-remove--other--self', i18n, [
-          renderContact(from),
-        ]);
-      } else if (from) {
-        return renderString('GroupV2--member-remove--other--other', i18n, {
-          adminName: renderContact(from),
-          memberName: renderContact(conversationId),
-        });
-      } else {
-        return renderString('GroupV2--member-remove--other--unknown', i18n, [
-          renderContact(conversationId),
-        ]);
       }
+      return renderString('GroupV2--member-remove--you--unknown', i18n);
     }
+
+    if (fromYou) {
+      return renderString('GroupV2--member-remove--other--you', i18n, [
+        renderContact(conversationId),
+      ]);
+    }
+    if (from && from === conversationId) {
+      return renderString('GroupV2--member-remove--other--self', i18n, [
+        renderContact(from),
+      ]);
+    }
+    if (from) {
+      return renderString('GroupV2--member-remove--other--other', i18n, {
+        adminName: renderContact(from),
+        memberName: renderContact(conversationId),
+      });
+    }
+    return renderString('GroupV2--member-remove--other--unknown', i18n, [
+      renderContact(conversationId),
+    ]);
   } else if (detail.type === 'member-privilege') {
     const { conversationId, newPrivilege } = detail;
     const weAreMember = conversationId === ourConversationId;
@@ -256,37 +250,38 @@ export function renderChangeDetail(
             i18n,
             [renderContact(from)]
           );
-        } else {
-          return renderString(
-            'GroupV2--member-privilege--promote--you--unknown',
-            i18n
-          );
-        }
-      } else {
-        if (fromYou) {
-          return renderString(
-            'GroupV2--member-privilege--promote--other--you',
-            i18n,
-            [renderContact(conversationId)]
-          );
-        } else if (from) {
-          return renderString(
-            'GroupV2--member-privilege--promote--other--other',
-            i18n,
-            {
-              adminName: renderContact(from),
-              memberName: renderContact(conversationId),
-            }
-          );
-        } else {
-          return renderString(
-            'GroupV2--member-privilege--promote--other--unknown',
-            i18n,
-            [renderContact(conversationId)]
-          );
         }
+
+        return renderString(
+          'GroupV2--member-privilege--promote--you--unknown',
+          i18n
+        );
       }
-    } else if (newPrivilege === RoleEnum.DEFAULT) {
+
+      if (fromYou) {
+        return renderString(
+          'GroupV2--member-privilege--promote--other--you',
+          i18n,
+          [renderContact(conversationId)]
+        );
+      }
+      if (from) {
+        return renderString(
+          'GroupV2--member-privilege--promote--other--other',
+          i18n,
+          {
+            adminName: renderContact(from),
+            memberName: renderContact(conversationId),
+          }
+        );
+      }
+      return renderString(
+        'GroupV2--member-privilege--promote--other--unknown',
+        i18n,
+        [renderContact(conversationId)]
+      );
+    }
+    if (newPrivilege === RoleEnum.DEFAULT) {
       if (weAreMember) {
         if (from) {
           return renderString(
@@ -294,41 +289,39 @@ export function renderChangeDetail(
             i18n,
             [renderContact(from)]
           );
-        } else {
-          return renderString(
-            'GroupV2--member-privilege--demote--you--unknown',
-            i18n
-          );
-        }
-      } else {
-        if (fromYou) {
-          return renderString(
-            'GroupV2--member-privilege--demote--other--you',
-            i18n,
-            [renderContact(conversationId)]
-          );
-        } else if (from) {
-          return renderString(
-            'GroupV2--member-privilege--demote--other--other',
-            i18n,
-            {
-              adminName: renderContact(from),
-              memberName: renderContact(conversationId),
-            }
-          );
-        } else {
-          return renderString(
-            'GroupV2--member-privilege--demote--other--unknown',
-            i18n,
-            [renderContact(conversationId)]
-          );
         }
+        return renderString(
+          'GroupV2--member-privilege--demote--you--unknown',
+          i18n
+        );
       }
-    } else {
-      throw new Error(
-        `member-privilege change type, privilege ${newPrivilege} is unknown`
+
+      if (fromYou) {
+        return renderString(
+          'GroupV2--member-privilege--demote--other--you',
+          i18n,
+          [renderContact(conversationId)]
+        );
+      }
+      if (from) {
+        return renderString(
+          'GroupV2--member-privilege--demote--other--other',
+          i18n,
+          {
+            adminName: renderContact(from),
+            memberName: renderContact(conversationId),
+          }
+        );
+      }
+      return renderString(
+        'GroupV2--member-privilege--demote--other--unknown',
+        i18n,
+        [renderContact(conversationId)]
       );
     }
+    throw new Error(
+      `member-privilege change type, privilege ${newPrivilege} is unknown`
+    );
   } else if (detail.type === 'pending-add-one') {
     const { conversationId } = detail;
     const weAreInvited = conversationId === ourConversationId;
@@ -337,22 +330,20 @@ export function renderChangeDetail(
         return renderString('GroupV2--pending-add--one--you--other', i18n, [
           renderContact(from),
         ]);
-      } else {
-        return renderString('GroupV2--pending-add--one--you--unknown', i18n);
-      }
-    } else {
-      if (fromYou) {
-        return renderString('GroupV2--pending-add--one--other--you', i18n, [
-          renderContact(conversationId),
-        ]);
-      } else if (from) {
-        return renderString('GroupV2--pending-add--one--other--other', i18n, [
-          renderContact(from),
-        ]);
-      } else {
-        return renderString('GroupV2--pending-add--one--other--unknown', i18n);
       }
+      return renderString('GroupV2--pending-add--one--you--unknown', i18n);
     }
+    if (fromYou) {
+      return renderString('GroupV2--pending-add--one--other--you', i18n, [
+        renderContact(conversationId),
+      ]);
+    }
+    if (from) {
+      return renderString('GroupV2--pending-add--one--other--other', i18n, [
+        renderContact(from),
+      ]);
+    }
+    return renderString('GroupV2--pending-add--one--other--unknown', i18n);
   } else if (detail.type === 'pending-add-many') {
     const { count } = detail;
 
@@ -360,16 +351,16 @@ export function renderChangeDetail(
       return renderString('GroupV2--pending-add--many--you', i18n, [
         count.toString(),
       ]);
-    } else if (from) {
+    }
+    if (from) {
       return renderString('GroupV2--pending-add--many--other', i18n, {
         memberName: renderContact(from),
         count: count.toString(),
       });
-    } else {
-      return renderString('GroupV2--pending-add--many--unknown', i18n, [
-        count.toString(),
-      ]);
     }
+    return renderString('GroupV2--pending-add--many--unknown', i18n, [
+      count.toString(),
+    ]);
   } else if (detail.type === 'pending-remove-one') {
     const { inviter, conversationId } = detail;
     const weAreInviter = Boolean(inviter && inviter === ourConversationId);
@@ -380,13 +371,15 @@ export function renderChangeDetail(
         return renderString('GroupV2--pending-remove--decline--you', i18n, [
           renderContact(conversationId),
         ]);
-      } else if (fromYou) {
+      }
+      if (fromYou) {
         return renderString(
           'GroupV2--pending-remove--revoke-invite-from-you--one--you',
           i18n,
           [renderContact(conversationId)]
         );
-      } else if (from) {
+      }
+      if (from) {
         return renderString(
           'GroupV2--pending-remove--revoke-invite-from-you--one--other',
           i18n,
@@ -395,29 +388,30 @@ export function renderChangeDetail(
             inviteeName: renderContact(conversationId),
           }
         );
-      } else {
-        return renderString(
-          'GroupV2--pending-remove--revoke-invite-from-you--one--unknown',
-          i18n,
-          [renderContact(conversationId)]
-        );
       }
-    } else if (sentByInvited) {
+      return renderString(
+        'GroupV2--pending-remove--revoke-invite-from-you--one--unknown',
+        i18n,
+        [renderContact(conversationId)]
+      );
+    }
+    if (sentByInvited) {
       if (inviter) {
         return renderString('GroupV2--pending-remove--decline--other', i18n, [
           renderContact(inviter),
         ]);
-      } else {
-        return renderString('GroupV2--pending-remove--decline--unknown', i18n);
       }
-    } else if (inviter) {
+      return renderString('GroupV2--pending-remove--decline--unknown', i18n);
+    }
+    if (inviter) {
       if (fromYou) {
         return renderString(
           'GroupV2--pending-remove--revoke-invite-from--one--you',
           i18n,
           [renderContact(inviter)]
         );
-      } else if (from) {
+      }
+      if (from) {
         return renderString(
           'GroupV2--pending-remove--revoke-invite-from--one--other',
           i18n,
@@ -426,29 +420,22 @@ export function renderChangeDetail(
             memberName: renderContact(inviter),
           }
         );
-      } else {
-        return renderString(
-          'GroupV2--pending-remove--revoke-invite-from--one--unknown',
-          i18n,
-          [renderContact(inviter)]
-        );
-      }
-    } else {
-      if (fromYou) {
-        return renderString('GroupV2--pending-remove--revoke--one--you', i18n);
-      } else if (from) {
-        return renderString(
-          'GroupV2--pending-remove--revoke--one--other',
-          i18n,
-          [renderContact(from)]
-        );
-      } else {
-        return renderString(
-          'GroupV2--pending-remove--revoke--one--unknown',
-          i18n
-        );
       }
+      return renderString(
+        'GroupV2--pending-remove--revoke-invite-from--one--unknown',
+        i18n,
+        [renderContact(inviter)]
+      );
     }
+    if (fromYou) {
+      return renderString('GroupV2--pending-remove--revoke--one--you', i18n);
+    }
+    if (from) {
+      return renderString('GroupV2--pending-remove--revoke--one--other', i18n, [
+        renderContact(from),
+      ]);
+    }
+    return renderString('GroupV2--pending-remove--revoke--one--unknown', i18n);
   } else if (detail.type === 'pending-remove-many') {
     const { count, inviter } = detail;
     const weAreInviter = Boolean(inviter && inviter === ourConversationId);
@@ -460,7 +447,8 @@ export function renderChangeDetail(
           i18n,
           [count.toString()]
         );
-      } else if (from) {
+      }
+      if (from) {
         return renderString(
           'GroupV2--pending-remove--revoke-invite-from-you--many--other',
           i18n,
@@ -469,14 +457,14 @@ export function renderChangeDetail(
             count: count.toString(),
           }
         );
-      } else {
-        return renderString(
-          'GroupV2--pending-remove--revoke-invite-from-you--many--unknown',
-          i18n,
-          [count.toString()]
-        );
       }
-    } else if (inviter) {
+      return renderString(
+        'GroupV2--pending-remove--revoke-invite-from-you--many--unknown',
+        i18n,
+        [count.toString()]
+      );
+    }
+    if (inviter) {
       if (fromYou) {
         return renderString(
           'GroupV2--pending-remove--revoke-invite-from--many--you',
@@ -486,7 +474,8 @@ export function renderChangeDetail(
             memberName: renderContact(inviter),
           }
         );
-      } else if (from) {
+      }
+      if (from) {
         return renderString(
           'GroupV2--pending-remove--revoke-invite-from--many--other',
           i18n,
@@ -496,40 +485,36 @@ export function renderChangeDetail(
             memberName: renderContact(inviter),
           }
         );
-      } else {
-        return renderString(
-          'GroupV2--pending-remove--revoke-invite-from--many--unknown',
-          i18n,
-          {
-            count: count.toString(),
-            memberName: renderContact(inviter),
-          }
-        );
-      }
-    } else {
-      if (fromYou) {
-        return renderString(
-          'GroupV2--pending-remove--revoke--many--you',
-          i18n,
-          [count.toString()]
-        );
-      } else if (from) {
-        return renderString(
-          'GroupV2--pending-remove--revoke--many--other',
-          i18n,
-          {
-            memberName: renderContact(from),
-            count: count.toString(),
-          }
-        );
-      } else {
-        return renderString(
-          'GroupV2--pending-remove--revoke--many--unknown',
-          i18n,
-          [count.toString()]
-        );
       }
+      return renderString(
+        'GroupV2--pending-remove--revoke-invite-from--many--unknown',
+        i18n,
+        {
+          count: count.toString(),
+          memberName: renderContact(inviter),
+        }
+      );
     }
+    if (fromYou) {
+      return renderString('GroupV2--pending-remove--revoke--many--you', i18n, [
+        count.toString(),
+      ]);
+    }
+    if (from) {
+      return renderString(
+        'GroupV2--pending-remove--revoke--many--other',
+        i18n,
+        {
+          memberName: renderContact(from),
+          count: count.toString(),
+        }
+      );
+    }
+    return renderString(
+      'GroupV2--pending-remove--revoke--many--unknown',
+      i18n,
+      [count.toString()]
+    );
   } else {
     throw missingCaseError(detail);
   }
diff --git a/ts/groups.ts b/ts/groups.ts
index 895801144713..4124403a1648 100644
--- a/ts/groups.ts
+++ b/ts/groups.ts
@@ -1,5 +1,3 @@
-/* tslint:disable no-dynamic-delete no-unnecessary-local-variable */
-
 import {
   compact,
   Dictionary,
@@ -8,6 +6,8 @@ import {
   isNumber,
   values,
 } from 'lodash';
+import { ClientZkGroupCipher } from 'zkgroup';
+import { v4 as getGuid } from 'uuid';
 import {
   getCredentialsForToday,
   GROUP_CREDENTIALS_KEY,
@@ -33,7 +33,6 @@ import {
   getClientZkAuthOperations,
   getClientZkGroupCipher,
 } from './util/zkgroup';
-import { ClientZkGroupCipher } from 'zkgroup';
 import {
   arrayBufferToBase64,
   arrayBufferToHex,
@@ -50,7 +49,6 @@ import {
   ProtoBinaryType,
 } from './textsecure.d';
 import { GroupCredentialsType } from './textsecure/WebAPI';
-import { v4 as getGuid } from 'uuid';
 import { CURRENT_SCHEMA_VERSION as MAX_MESSAGE_SCHEMA } from '../js/modules/types/message';
 
 export type GroupV2AccessAttributesChangeType = {
@@ -250,7 +248,9 @@ export async function uploadGroupChange({
 
 // Utility
 
-export function deriveGroupFields(masterKey: ArrayBuffer) {
+export function deriveGroupFields(
+  masterKey: ArrayBuffer
+): Record<string, ArrayBuffer> {
   const secretParams = deriveGroupSecretParams(masterKey);
   const publicParams = deriveGroupPublicParams(secretParams);
   const id = deriveGroupID(secretParams);
@@ -273,7 +273,9 @@ type MaybeUpdatePropsType = {
   dropInitialJoinMessage?: boolean;
 };
 
-export async function waitThenMaybeUpdateGroup(options: MaybeUpdatePropsType) {
+export async function waitThenMaybeUpdateGroup(
+  options: MaybeUpdatePropsType
+): Promise<void> {
   // First wait to process all incoming messages on the websocket
   await window.waitForEmptyEventQueue();
 
@@ -321,8 +323,9 @@ export async function maybeUpdateGroup({
 
     conversation.set(newAttributes);
 
-    // Ensure that all generated message are ordered properly. Before the provided timestamp
-    //   so update messages appear before the initiating message, or after now().
+    // Ensure that all generated messages are ordered properly.
+    // Before the provided timestamp so update messages appear before the
+    //   initiating message, or after now().
     let syntheticTimestamp = receivedAt
       ? receivedAt - (groupChangeMessages.length + 1)
       : Date.now();
@@ -355,7 +358,6 @@ export async function maybeUpdateGroup({
       const contact = window.ConversationController.get(member.uuid);
 
       if (member.profileKey && contact && !contact.get('profileKey')) {
-        // tslint:disable-next-line no-floating-promises
         contact.setProfileKey(member.profileKey);
       }
     });
@@ -487,8 +489,8 @@ async function updateGroupViaState({
           authCredentialBase64: groupCredentials.tomorrow.credential,
         });
         return result;
-      } catch (error) {
-        if (error.code === GROUP_ACCESS_DENIED_CODE) {
+      } catch (subError) {
+        if (subError.code === GROUP_ACCESS_DENIED_CODE) {
           return generateLeftGroupChanges(group);
         }
       }
@@ -537,9 +539,8 @@ async function updateGroupViaLogs({
         ...deltaOptions,
         authCredentialBase64: groupCredentials.tomorrow.credential,
       });
-    } else {
-      throw error;
     }
+    throw error;
   }
 }
 
@@ -654,6 +655,7 @@ async function getGroupDelta({
   let response;
   const changes: Array<GroupChangesClass> = [];
   do {
+    // eslint-disable-next-line no-await-in-loop
     response = await sender.getGroupLog(revisionToFetch, options);
     changes.push(response.changes);
     if (response.end) {
@@ -689,6 +691,7 @@ async function integrateGroupChanges({
     const { groupChanges } = changes[i];
 
     if (!groupChanges) {
+      // eslint-disable-next-line no-continue
       continue;
     }
 
@@ -699,6 +702,7 @@ async function integrateGroupChanges({
       const { groupChange } = changeState;
 
       if (!groupChange) {
+        // eslint-disable-next-line no-continue
         continue;
       }
 
@@ -707,6 +711,7 @@ async function integrateGroupChanges({
           newAttributes,
           groupChangeMessages,
           members,
+          // eslint-disable-next-line no-await-in-loop
         } = await integrateGroupChange({
           group: attributes,
           newRevision,
@@ -868,7 +873,6 @@ export async function getCurrentGroupState({
   };
 }
 
-// tslint:disable-next-line max-func-body-length cyclomatic-complexity
 function extractDiffs({
   current,
   dropInitialJoinMessage,
@@ -1126,7 +1130,6 @@ type GroupChangeResultType = {
   newProfileKeys: Array<GroupChangeMemberType>;
 };
 
-// tslint:disable-next-line cyclomatic-complexity max-func-body-length
 async function applyGroupChange({
   group,
   actions,
@@ -1158,7 +1161,7 @@ async function applyGroupChange({
   result.revision = version;
 
   // addMembers?: Array<GroupChangeClass.Actions.AddMemberAction>;
-  (actions.addMembers || []).map(addMember => {
+  (actions.addMembers || []).forEach(addMember => {
     const { added } = addMember;
     if (!added) {
       throw new Error('applyGroupChange: addMember.added is missing');
@@ -1249,7 +1252,8 @@ async function applyGroupChange({
     }
   });
 
-  // modifyMemberProfileKeys?: Array<GroupChangeClass.Actions.ModifyMemberProfileKeyAction>;
+  // modifyMemberProfileKeys?:
+  // Array<GroupChangeClass.Actions.ModifyMemberProfileKeyAction>;
   (actions.modifyMemberProfileKeys || []).forEach(modifyMemberProfileKey => {
     const { profileKey, uuid } = modifyMemberProfileKey;
     if (!profileKey || !uuid) {
@@ -1374,8 +1378,7 @@ async function applyGroupChange({
 
   // modifyTitle?: GroupChangeClass.Actions.ModifyTitleAction;
   if (actions.modifyTitle) {
-    const title: GroupAttributeBlobClass | undefined =
-      actions.modifyTitle.title;
+    const { title } = actions.modifyTitle;
     if (title && title.content === 'title') {
       result.name = title.title;
     } else {
@@ -1388,11 +1391,12 @@ async function applyGroupChange({
 
   // modifyAvatar?: GroupChangeClass.Actions.ModifyAvatarAction;
   if (actions.modifyAvatar) {
-    const avatar = actions.modifyAvatar.avatar;
+    const { avatar } = actions.modifyAvatar;
     await applyNewAvatar(avatar, result, logId);
   }
 
-  // modifyDisappearingMessagesTimer?: GroupChangeClass.Actions.ModifyDisappearingMessagesTimerAction;
+  // modifyDisappearingMessagesTimer?:
+  // GroupChangeClass.Actions.ModifyDisappearingMessagesTimerAction;
   if (actions.modifyDisappearingMessagesTimer) {
     const disappearingMessagesTimer: GroupAttributeBlobClass | undefined =
       actions.modifyDisappearingMessagesTimer.timer;
@@ -1415,7 +1419,8 @@ async function applyGroupChange({
     attributes: ACCESS_ENUM.MEMBER,
   };
 
-  // modifyAttributesAccess?: GroupChangeClass.Actions.ModifyAttributesAccessControlAction;
+  // modifyAttributesAccess?:
+  // GroupChangeClass.Actions.ModifyAttributesAccessControlAction;
   if (actions.modifyAttributesAccess) {
     result.accessControl = {
       ...result.accessControl,
@@ -1447,6 +1452,8 @@ async function applyGroupChange({
   };
 }
 
+// Ovewriting result.avatar as part of functionality
+/* eslint-disable no-param-reassign */
 async function applyNewAvatar(
   newAvatar: string | undefined,
   result: ConversationAttributesType,
@@ -1514,8 +1521,8 @@ async function applyNewAvatar(
     result.avatar = undefined;
   }
 }
+/* eslint-enable no-param-reassign */
 
-// tslint:disable-next-line cyclomatic-complexity max-func-body-length
 async function applyGroupState(
   group: ConversationAttributesType,
   groupState: GroupClass
@@ -1532,7 +1539,7 @@ async function applyGroupState(
 
   // title
   // Note: During decryption, title becomes a GroupAttributeBlob
-  const title: GroupAttributeBlobClass | undefined = groupState.title;
+  const { title } = groupState;
   if (title && title.content === 'title') {
     result.name = title.title;
   } else {
@@ -1544,8 +1551,7 @@ async function applyGroupState(
 
   // disappearingMessagesTimer
   // Note: during decryption, disappearingMessageTimer becomes a GroupAttributeBlob
-  const disappearingMessagesTimer: GroupAttributeBlobClass | undefined =
-    groupState.disappearingMessagesTimer;
+  const { disappearingMessagesTimer } = groupState;
   if (
     disappearingMessagesTimer &&
     disappearingMessagesTimer.content === 'disappearingMessagesDuration'
@@ -1665,13 +1671,13 @@ function hasData(data: ProtoBinaryType): boolean {
   return data && data.limit > 0;
 }
 
-// tslint:disable-next-line max-func-body-length cyclomatic-complexity
 function decryptGroupChange(
-  actions: GroupChangeClass.Actions,
+  _actions: GroupChangeClass.Actions,
   groupSecretParams: string,
   logId: string
 ): GroupChangeClass.Actions {
   const clientZkGroupCipher = getClientZkGroupCipher(groupSecretParams);
+  const actions = _actions;
 
   if (hasData(actions.sourceUuid)) {
     try {
@@ -1701,7 +1707,9 @@ function decryptGroupChange(
 
   // addMembers?: Array<GroupChangeClass.Actions.AddMemberAction>;
   actions.addMembers = compact(
-    (actions.addMembers || []).map(addMember => {
+    (actions.addMembers || []).map(_addMember => {
+      const addMember = _addMember;
+
       if (addMember.added) {
         const decrypted = decryptMember(
           clientZkGroupCipher,
@@ -1714,17 +1722,16 @@ function decryptGroupChange(
 
         addMember.added = decrypted;
         return addMember;
-      } else {
-        throw new Error(
-          'decryptGroupChange: AddMember was missing added field!'
-        );
       }
+      throw new Error('decryptGroupChange: AddMember was missing added field!');
     })
   );
 
   // deleteMembers?: Array<GroupChangeClass.Actions.DeleteMemberAction>;
   actions.deleteMembers = compact(
-    (actions.deleteMembers || []).map(deleteMember => {
+    (actions.deleteMembers || []).map(_deleteMember => {
+      const deleteMember = _deleteMember;
+
       if (hasData(deleteMember.deletedUserId)) {
         try {
           deleteMember.deletedUserId = decryptUuid(
@@ -1764,7 +1771,9 @@ function decryptGroupChange(
 
   // modifyMemberRoles?: Array<GroupChangeClass.Actions.ModifyMemberRoleAction>;
   actions.modifyMemberRoles = compact(
-    (actions.modifyMemberRoles || []).map(modifyMember => {
+    (actions.modifyMemberRoles || []).map(_modifyMember => {
+      const modifyMember = _modifyMember;
+
       if (hasData(modifyMember.userId)) {
         try {
           modifyMember.userId = decryptUuid(
@@ -1808,9 +1817,12 @@ function decryptGroupChange(
     })
   );
 
-  // modifyMemberProfileKeys?: Array<GroupChangeClass.Actions.ModifyMemberProfileKeyAction>;
+  // modifyMemberProfileKeys?:
+  // Array<GroupChangeClass.Actions.ModifyMemberProfileKeyAction>;
   actions.modifyMemberProfileKeys = compact(
-    (actions.modifyMemberProfileKeys || []).map(modifyMemberProfileKey => {
+    (actions.modifyMemberProfileKeys || []).map(_modifyMemberProfileKey => {
+      const modifyMemberProfileKey = _modifyMemberProfileKey;
+
       if (hasData(modifyMemberProfileKey.presentation)) {
         const { profileKey, uuid } = decryptProfileKeyCredentialPresentation(
           clientZkGroupCipher,
@@ -1854,7 +1866,9 @@ function decryptGroupChange(
 
   // addPendingMembers?: Array<GroupChangeClass.Actions.AddPendingMemberAction>;
   actions.addPendingMembers = compact(
-    (actions.addPendingMembers || []).map(addPendingMember => {
+    (actions.addPendingMembers || []).map(_addPendingMember => {
+      const addPendingMember = _addPendingMember;
+
       if (addPendingMember.added) {
         const decrypted = decryptPendingMember(
           clientZkGroupCipher,
@@ -1867,17 +1881,18 @@ function decryptGroupChange(
 
         addPendingMember.added = decrypted;
         return addPendingMember;
-      } else {
-        throw new Error(
-          'decryptGroupChange: addPendingMember was missing added field!'
-        );
       }
+      throw new Error(
+        'decryptGroupChange: addPendingMember was missing added field!'
+      );
     })
   );
 
   // deletePendingMembers?: Array<GroupChangeClass.Actions.DeletePendingMemberAction>;
   actions.deletePendingMembers = compact(
-    (actions.deletePendingMembers || []).map(deletePendingMember => {
+    (actions.deletePendingMembers || []).map(_deletePendingMember => {
+      const deletePendingMember = _deletePendingMember;
+
       if (hasData(deletePendingMember.deletedUserId)) {
         try {
           deletePendingMember.deletedUserId = decryptUuid(
@@ -1917,7 +1932,9 @@ function decryptGroupChange(
 
   // promotePendingMembers?: Array<GroupChangeClass.Actions.PromotePendingMemberAction>;
   actions.promotePendingMembers = compact(
-    (actions.promotePendingMembers || []).map(promotePendingMember => {
+    (actions.promotePendingMembers || []).map(_promotePendingMember => {
+      const promotePendingMember = _promotePendingMember;
+
       if (hasData(promotePendingMember.presentation)) {
         const { profileKey, uuid } = decryptProfileKeyCredentialPresentation(
           clientZkGroupCipher,
@@ -1979,7 +1996,8 @@ function decryptGroupChange(
   // modifyAvatar?: GroupChangeClass.Actions.ModifyAvatarAction;
   // Note: decryption happens during application of the change, on download of the avatar
 
-  // modifyDisappearingMessagesTimer?: GroupChangeClass.Actions.ModifyDisappearingMessagesTimerAction;
+  // modifyDisappearingMessagesTimer?:
+  // GroupChangeClass.Actions.ModifyDisappearingMessagesTimerAction;
   if (
     actions.modifyDisappearingMessagesTimer &&
     hasData(actions.modifyDisappearingMessagesTimer.timer)
@@ -2002,7 +2020,8 @@ function decryptGroupChange(
     actions.modifyDisappearingMessagesTimer.timer = undefined;
   }
 
-  // modifyAttributesAccess?: GroupChangeClass.Actions.ModifyAttributesAccessControlAction;
+  // modifyAttributesAccess?:
+  // GroupChangeClass.Actions.ModifyAttributesAccessControlAction;
   if (
     actions.modifyAttributesAccess &&
     !isValidAccess(actions.modifyAttributesAccess.attributesAccess)
@@ -2025,13 +2044,13 @@ function decryptGroupChange(
   return actions;
 }
 
-// tslint:disable-next-line max-func-body-length
 function decryptGroupState(
-  groupState: GroupClass,
+  _groupState: GroupClass,
   groupSecretParams: string,
   logId: string
 ): GroupClass {
   const clientZkGroupCipher = getClientZkGroupCipher(groupSecretParams);
+  const groupState = _groupState;
 
   // title
   if (hasData(groupState.title)) {
@@ -2121,9 +2140,11 @@ function decryptGroupState(
 
 function decryptMember(
   clientZkGroupCipher: ClientZkGroupCipher,
-  member: MemberClass,
+  _member: MemberClass,
   logId: string
 ) {
+  const member = _member;
+
   // userId
   if (hasData(member.userId)) {
     try {
@@ -2175,12 +2196,13 @@ function decryptMember(
   return member;
 }
 
-// tslint:disable-next-line max-func-body-length cyclomatic-complexity
 function decryptPendingMember(
   clientZkGroupCipher: ClientZkGroupCipher,
-  member: PendingMemberClass,
+  _member: PendingMemberClass,
   logId: string
 ) {
+  const member = _member;
+
   // addedByUserId
   if (hasData(member.addedByUserId)) {
     try {
diff --git a/ts/model-types.d.ts b/ts/model-types.d.ts
index 4a606c3f33ca..6473edf9cc71 100644
--- a/ts/model-types.d.ts
+++ b/ts/model-types.d.ts
@@ -25,7 +25,7 @@ declare class DeletesModelType extends Backbone.Model<DeletesAttributesType> {
 
 type TaskResultType = any;
 
-type MessageAttributesType = {
+export type MessageAttributesType = {
   id: string;
   type?: string;
 
@@ -63,9 +63,9 @@ declare class MessageModelType extends Backbone.Model<MessageAttributesType> {
   ): Promise<void>;
 }
 
-type ConversationTypeType = 'private' | 'group';
+export type ConversationTypeType = 'private' | 'group';
 
-type ConversationAttributesType = {
+export type ConversationAttributesType = {
   id: string;
   type: ConversationTypeType;
   timestamp: number;
@@ -201,7 +201,7 @@ export declare class ConversationModelType extends Backbone.Model<
   wrapSend: (sendPromise: Promise<any>) => Promise<any>;
 }
 
-declare class ConversationModelCollectionType extends Backbone.Collection<
+export declare class ConversationModelCollectionType extends Backbone.Collection<
   ConversationModelType
 > {
   resetLookups(): void;
diff --git a/ts/textsecure.d.ts b/ts/textsecure.d.ts
index ee6f9a8f7062..a494741b5725 100644
--- a/ts/textsecure.d.ts
+++ b/ts/textsecure.d.ts
@@ -209,7 +209,7 @@ type ProtobufCollectionType = DeviceMessagesProtobufTypes &
 // Note: there are a lot of places in the code that overwrite a field like this
 //   with a type that the app can use. Being more rigorous with these
 //   types would require code changes, out of scope for now.
-type ProtoBinaryType = any;
+export type ProtoBinaryType = any;
 type ProtoBigNumberType = any;
 
 // Groups.proto
diff --git a/tslint.json b/tslint.json
index eefe15e091d9..8cd695ffce98 100644
--- a/tslint.json
+++ b/tslint.json
@@ -177,6 +177,7 @@
   "rulesDirectory": ["node_modules/tslint-microsoft-contrib"],
   "linterOptions": {
     "exclude": [
+      "ts/*.ts",
       "ts/components/emoji/**",
       "ts/backbone/**",
       "ts/build/**",