Migrating a React Native Project from JavaScript to TypeScript: A Step-by-Step Guide

TL;DR

• Why migrate? TypeScript reduces runtime errors, improves DX, and makes large React Native apps easier to maintain.
  
• Setup first: Install TypeScript, add tsconfig.json, and enable hybrid JS/TS environment.
  
• Migrate gradually: Rename .js to .ts/.tsx, start with isolated modules, then scale to Redux, navigation, and forms.
  
• Add type safety: Use interfaces, @types packages, and custom declarations for untyped libraries.
  
• Best practices: Use ESLint + Prettier, set migration goals, and get expert help if needed for complex projects.

Introduction

React Native has established itself as one of the leading frameworks for building cross-platform mobile applications, allowing developers to create performant apps for iOS and Android with a single codebase. While JavaScript has powered much of its success, the dynamic nature of JavaScript can quickly become a bottleneck as projects scale. Large codebases often face challenges such as inconsistent data handling, hidden runtime errors, and difficulties in maintaining code quality across teams.

This is where TypeScript makes a real difference. By introducing static type checking, TypeScript helps catch errors at compile-time instead of letting them slip into production. It also enhances developer productivity with better auto-completion, IntelliSense, and safe refactoring tools. For teams working on medium to enterprise-level applications, the shift from JavaScript to TypeScript translates into improved collaboration, easier onboarding of new developers, and a more maintainable project in the long run.

Migrating a React Native project doesn’t have to be overwhelming. With the right strategy and support from an experienced React Native app development company – you can make the transition smooth, future-proof your application, and unlock the full benefits of TypeScript. In this guide, we’ll take you through the step-by-step process of migrating confidently, even in production-ready apps.

Why Migrate to TypeScript?

• Improved Developer Experience: Auto-completion, refactoring, and better IntelliSense.
  
• Reduced Bugs: Type safety catches common errors at compile-time.
  
• Easier Refactoring: Confidently refactor large codebases.
  
• Better Documentation: Types serve as implicit documentation.
  

Step by Step guide to Migrate React Native Project from JavaScript to TypeScript

Step 1: Set Up TypeScript in Your React Native Project

First, install the necessary TypeScript dependencies:

npm install --save-dev typescript @types/react @types/react-native

Then create a tsconfig.json:

{

 "compilerOptions": {

   "target": "esnext",

   "module": "commonjs",

   "strict": true,

   "jsx": "react-native",

   "moduleResolution": "node",

   "allowJs": true,

   "noEmit": true,

   "isolatedModules": true

 },

 "exclude": ["node_modules", "babel.config.js", "metro.config.js", "jest.config.js"]

}

This configuration allows a hybrid environment where both .js and .ts files can co-exist.

Step 2: Begin Gradual Migration

Start by renaming one .js file to .tsx (for components) or .ts (for utilities).

Example:

Rename App.js to App.tsx, then update the file:

import React from 'react';

import { View, Text } from 'react-native';

const App: React.FC = () => {

 return (

   <View>

     <Text>Welcome to TypeScript!</Text>

   </View>

 );

};

export default App;

Work module-by-module. Migrate isolated parts first like helper functions and UI components.

Step 3: Add Type Definitions

Install types for third-party libraries:

npm install --save-dev @types/react-navigation

If a library has no types:

// declaration.d.ts

declare module 'some-untype-lib';

Use interfaces and types for props, state, API responses:

type User = {

 id: number;

 name: string;

 email: string;

};

Step 4: TypeScript with Navigation, Redux & Forms

• React Navigation: Use type-safe params.
  
• Redux Toolkit: Add type-safe states and actions.
  
• Forms: Combine Formik with Yup or Zod for validation.

Example Redux Slice:

interface AuthState {

 isLoggedIn: boolean;

 user: User | null;

}

Step 5: Setup ESLint + Prettier for TypeScript

Ensure code quality with linting:

npm install --save-dev eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin

Example .eslintrc.js:

module.exports = {

 parser: '@typescript-eslint/parser',

 plugins: ['@typescript-eslint'],

 extends: ['plugin:@typescript-eslint/recommended'],

};

Step 6: Enforce TypeScript Gradually

Keep “allowJs”: true in your tsconfig.json until you’re fully migrated.
Set goals like:

• Migrate 3 files per day
  
• Add types to Redux store by end of week
  
• Fully convert utilities folder in first sprint

Conclusion

Migrating a React Native project from JavaScript to TypeScript strengthens your codebase with type safety, fewer runtime errors, and better developer experience. Static typing enables safer refactoring, clearer contracts, and faster onboarding without affecting runtime performance. Approach the transition incrementally: enable TypeScript, convert leaf modules, and add types to navigation, state, and API layers so timelines stay predictable. Complexities often appear with third party libraries or shared schemas; expert guidance prevents stalls. If you are planning this shift, consider partnering with specialists you can hire React Native developers for a seamless, production ready migration and claim a free 30 minute consultation.

FAQs

Q1: Is it necessary to convert the whole project at once?

No, TypeScript allows gradual migration. You can use .js and .ts files together initially.

Q2: Does TypeScript impact app performance?

No, TypeScript is removed at compile-time and doesn’t affect runtime performance.

Q3: What’s the best way to learn TypeScript while migrating?

Start by converting small components and use VSCode with TypeScript plugins for inline help.

Q4: Can I skip types for external libraries?

Yes, but it’s not recommended. You can write minimal custom type declarations if needed.

Q5: Will I need to rewrite my Redux or Navigation setup?

No, you can keep your logic and add typings incrementally.

React Native

Sagar Makwana

Software Engineer