diff --git a/src/App.tsx b/src/App.tsx
index fd7b152..d317287 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -2,14 +2,15 @@ import { useState } from 'react';
 import { faker } from '@faker-js/faker';
 import { TodoItem } from './TodoItem';
 import { nanoid } from 'nanoid';
+import { ReactElement } from 'react';
 
-const generateFakeTodoItem = () => ({
+const generateFakeTodoItem = (): { label: string; status: string; id: string; } => ({
   label: faker.hacker.phrase(),
   status: faker.random.arrayElement(['open', 'done', 'archived']),
   id: nanoid(),
 });
 
-const generateNTodo = (size) => {
+const generateNTodo = (size: number): { label: string; status: string; id: string; }[] => {
   return Array.from(Array(size).keys()).map(generateFakeTodoItem);
 };
 
@@ -32,10 +33,10 @@ const initialList = [
   ...generateNTodo(10),
 ];
 
-function App() {
+function App(): ReactElement  {
   const [todoList, setTodoList] = useState(initialList);
 
-  const updater = (id, newStatus) => {
+  const updater = (id: string, newStatus: string): void => {
     setTodoList((oldList) =>
       oldList.map((it) => {
         if (it.id !== id) {
@@ -57,7 +58,7 @@ function App() {
             key={item.id}
             label={item.label}
             status={item.status}
-            onChecked={(newState) => updater(item.id, newState)}
+            onChecked={(newState: string):void => updater(item.id, newState)}
           />
         ))}
       </div>
diff --git a/src/TodoItem.tsx b/src/TodoItem.tsx
index d52e923..35ccd60 100644
--- a/src/TodoItem.tsx
+++ b/src/TodoItem.tsx
@@ -1,6 +1,7 @@
 import clsx from 'clsx';
+import { ReactElement } from 'react';
 
-export const TodoItem = ({ status, label, onChecked }) => {
+export const TodoItem = ({ status, label, onChecked }: { status: string; label: string; onChecked:(status: string) => void; }): ReactElement => {
   return (
     <div
       className={clsx('p-4 flex items-center', {
@@ -17,7 +18,7 @@ export const TodoItem = ({ status, label, onChecked }) => {
         disabled={status === 'archived'}
         type="checkbox"
         className="rounded text-pink-500 ml-8 cursor-pointer disabled:cursor-not-allowed disabled:bg-black disabled:hover:bg-black"
-        onChange={() => onChecked(status === 'open' ? 'done' : 'open')}
+        onChange={(): void => onChecked(status === 'open' ? 'done' : 'open')}
       />
     </div>
   );