diff --git a/src/libs/ActiveClientManager/index.native.js b/src/libs/ActiveClientManager/index.native.js
deleted file mode 100644
index c86f847a1a6e..000000000000
--- a/src/libs/ActiveClientManager/index.native.js
+++ /dev/null
@@ -1,14 +0,0 @@
-/**
- * For native devices, there will never be more than one
- * client running at a time, so this lib is a big no-op
- */
-
-function init() {}
-function isClientTheLeader() {
-    return true;
-}
-function isReady() {
-    return Promise.resolve();
-}
-
-export {init, isReady, isClientTheLeader};
diff --git a/src/libs/ActiveClientManager/index.native.ts b/src/libs/ActiveClientManager/index.native.ts
new file mode 100644
index 000000000000..1d455a84a28a
--- /dev/null
+++ b/src/libs/ActiveClientManager/index.native.ts
@@ -0,0 +1,14 @@
+/**
+ * For native devices, there will never be more than one
+ * client running at a time, so this lib is a big no-op
+ */
+
+import {Init, IsReady, IsClientTheLeader} from './types';
+
+const init: Init = () => {};
+
+const isClientTheLeader: IsClientTheLeader = () => true;
+
+const isReady: IsReady = () => Promise.resolve();
+
+export {init, isClientTheLeader, isReady};
diff --git a/src/libs/ActiveClientManager/index.js b/src/libs/ActiveClientManager/index.ts
similarity index 77%
rename from src/libs/ActiveClientManager/index.js
rename to src/libs/ActiveClientManager/index.ts
index 2117e5dac373..f99f54e84aa5 100644
--- a/src/libs/ActiveClientManager/index.js
+++ b/src/libs/ActiveClientManager/index.ts
@@ -4,27 +4,24 @@
  * This file ensures exactly that by tracking all the clientIDs connected, storing the most recent one last and it considers that last clientID the "leader".
  */
 
-import _ from 'underscore';
 import Onyx from 'react-native-onyx';
 import Str from 'expensify-common/lib/str';
 import ONYXKEYS from '../../ONYXKEYS';
 import * as ActiveClients from '../actions/ActiveClients';
+import {Init, IsReady, IsClientTheLeader} from './types';
 
 const clientID = Str.guid();
 const maxClients = 20;
-let activeClients = [];
-let resolveSavedSelfPromise;
-const savedSelfPromise = new Promise((resolve) => {
+let activeClients: string[] = [];
+let resolveSavedSelfPromise: () => void;
+const savedSelfPromise = new Promise<void>((resolve) => {
     resolveSavedSelfPromise = resolve;
 });
 
 /**
  * Determines when the client is ready. We need to wait both till we saved our ID in onyx AND the init method was called
- * @returns {Promise}
  */
-function isReady() {
-    return savedSelfPromise;
-}
+const isReady: IsReady = () => savedSelfPromise;
 
 Onyx.connect({
     key: ONYXKEYS.ACTIVE_CLIENTS,
@@ -53,19 +50,19 @@ Onyx.connect({
  * Add our client ID to the list of active IDs.
  * We want to ensure we have no duplicates and that the activeClient gets added at the end of the array (see isClientTheLeader)
  */
-function init() {
-    activeClients = _.without(activeClients, clientID);
+const init: Init = () => {
+    activeClients = activeClients.filter((id) => id !== clientID);
     activeClients.push(clientID);
     ActiveClients.setActiveClients(activeClients).then(resolveSavedSelfPromise);
-}
+};
 
 /**
  * The last GUID is the most recent GUID, so that should be the leader
- *
- * @returns {Boolean}
  */
-function isClientTheLeader() {
-    return _.last(activeClients) === clientID;
-}
+const isClientTheLeader: IsClientTheLeader = () => {
+    const lastActiveClient = activeClients.length && activeClients[activeClients.length - 1];
+
+    return lastActiveClient === clientID;
+};
 
 export {init, isClientTheLeader, isReady};
diff --git a/src/libs/ActiveClientManager/types.ts b/src/libs/ActiveClientManager/types.ts
new file mode 100644
index 000000000000..a5c7d1e6d721
--- /dev/null
+++ b/src/libs/ActiveClientManager/types.ts
@@ -0,0 +1,7 @@
+type Init = () => void;
+
+type IsClientTheLeader = () => boolean;
+
+type IsReady = () => Promise<void>;
+
+export type {Init, IsClientTheLeader, IsReady};