Using TypeScript

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An in-depth guide on configuring an Expo project with TypeScript.

Expo has first-class support for TypeScript. The JavaScript interface of Expo SDK is written in TypeScript.

This guide provides a quick way to get started for a new project and also steps to migrate your existing JavaScript based Expo project to use TypeScript.

Quick start

To create a new project, use the default template which includes base TypeScript configuration, example code, and basic navigation structure:

Terminal

- npx create-expo-app@latest

After you create a new project using the command above, make sure to follow instructions from:

Set up your environment which provides required steps for setting local development environment.
Start developing which provides information on triggering a development server, file structure, and details about other features.

Migrating existing JavaScript project

To migrate your existing JavaScript based project to use TypeScript, follow the instructions below:

Rename files to use .tsx or .ts extension

Rename files to convert them to TypeScript. For example, start with the root component file such as App.js and rename it to App.tsx:

Terminal

- mv App.js App.tsx

Tip: Use the .tsx extension if the file includes React components (JSX). If the file does not include any JSX, you can use the .ts file extension.

Install required development dependencies

To install required devDependencies such as typescript and @types/react in package.json:

Terminal

- npx expo install typescript @types/react --dev

Terminal

- npx expo install typescript @types/react "--" --dev

Alternatively, run npx expo start command to install typescript and @types/react dev dependencies.

Type checking project files with tsc

To type check your project's files run tsc command within the root of your project directory:

Terminal

# For npm

- npm run tsc

# For yarn

- yarn tsc

Add base configuration with tsconfig.json

A project's tsconfig.json should extend expo/tsconfig.base by default. You can automatically generate a tsconfig.json file by running the command:

Terminal

- npx expo customize tsconfig.json

The default configuration in tsconfig.json is user-friendly and encourages adoption. If you prefer strict type checking and reduce the chances of runtime errors, enable strict under compilerOptions:

tsconfig.json

{
  "extends": "expo/tsconfig.base",
  "compilerOptions": {
    "strict": true
  }
}

Path aliases (Optional)

Expo CLI supports path aliases in tsconfig.json automatically. It allows importing modules with custom aliases instead of relative paths.

For example, to import Button component from src/components/Button.tsx using the alias @/components/Button, add the alias @/* in tsconfig.json and set it to the src directory:

tsconfig.json

{
  "extends": "expo/tsconfig.base",
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"]
    }
  }
}

Disable path aliases

tsconfigPaths is enabled by default which allows you to set path aliases. You can disable it by setting tsconfigPaths to false in the project's app config:

app.json

{
  "expo": {
    "experiments": {
      "tsconfigPaths": false
    }
  }
}

Considerations

When using path aliases, consider the following:

Restart Expo CLI after modifying tsconfig.json to update path aliases. You don't need to clear the Metro cache when the aliases change.
If not using TypeScript, jsconfig.json can serve as an alternative to tsconfig.json.
Path aliases add additional resolution time when defined.
Path aliases are only supported by Metro (including Metro web) and not by the deprecated @expo/webpack-config.
Bare projects require additional setup for this feature. See the Metro setup guide for more information.

Absolute imports (Optional)

To enable absolute imports from a project's root directory, define compilerOptions.baseUrl the tsconfig.json file:

tsconfig.json

{
  "extends": "expo/tsconfig.base",
  "compilerOptions": {
    "baseUrl": "./"
  }
}

For example, setting the above configuration allows importing Button component from the path src/components/Button:

import Button from 'src/components/Button';

Considerations

When using absolute imports, consider the following:

compilerOptions.paths are resolved relative to the compilerOptions.baseUrl if it is defined, otherwise they're resolved against the project root directory.
compilerOptions.baseUrl is resolved before node modules. This means if you have a file named ./path.ts, it can be imported instead of a node module named path.
Restarting Expo CLI is necessary to update compilerOptions.baseUrl after modifying the tsconfig.json.
If you're not using TypeScript, jsconfig.json can serve as an alternative to tsconfig.json.
Absolute imports are only supported by Metro (including Metro web) and not by @expo/webpack-config.
Bare projects require additional setup for this feature. See the versioned Metro setup guide for more information.

Type generation

Some Expo libraries provide both static types and type generation capabilities. These types are automatically generated when the project builds or by running the npx expo customize tsconfig.json command.

TypeScript for project's config files

Additional setup is required to use TypeScript for configuration files such as metro.config.js or app.config.js. You need to utilize ts-node require hook to import TypeScript files within your JS config file. This hook allows TypeScript imports while keeping the root file as JavaScript.

Terminal

- npx expo install ts-node --dev

Terminal

- npx expo install ts-node "--" --dev

metro.config.js

Update metro.config.js to require metro.config.ts file:

metro.config.js

require('ts-node/register');
module.exports = require('./metro.config.ts');

Update metro.config.ts file with your project's metro configuration:

metro.config.ts

import { getDefaultConfig } from 'expo/metro-config';

const config = getDefaultConfig(__dirname);

module.exports = config;

Deprecated: webpack.config.js

Install the @expo/webpack-config package.

webpack.config.js

require('ts-node/register');
module.exports = require('./webpack.config.ts');

webpack.config.ts

import createExpoWebpackConfigAsync from '@expo/webpack-config/webpack';
import { Arguments, Environment } from '@expo/webpack-config/webpack/types';

module.exports = async function (env: Environment, argv: Arguments) {
  const config = await createExpoWebpackConfigAsync(env, argv);
  // Customize the config before returning it.
  return config;
};

app.config.js

app.config.ts is supported by default. However, it doesn't support external TypeScript modules, or tsconfig.json customization. You can use the following approach to get a more comprehensive TypeScript setup:

app.config.ts

import 'ts-node/register'; // Add this to import TypeScript files
import { ExpoConfig } from 'expo/config';

const config: ExpoConfig = {
  name: 'my-app',
  slug: 'my-app',
};

export default config;

Other TypeScript features

Some language features may require additional configuration. For example, if you want to use decorators you'll need to add the experimentalDecorators option. For more information on the available properties see the TypeScript compiler options documentation.

Learn how to use TypeScript

A good place to start learning TypeScript is the official TypeScript Handbook.

For TypeScript and React components, we recommend referring to the React TypeScript CheatSheet to learn how to type your React components in a variety of common situations.