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An in-depth guide on configuring an Expo project with TypeScript.
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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.
To create a new project, use the default template which includes base TypeScript configuration, example code, and basic navigation structure:
-Â npx create-expo-app@latestAfter you create a new project using the command above, make sure to follow instructions from:
To migrate your existing JavaScript based project to use TypeScript, follow the instructions below:
1
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:
-Â mv App.js App.tsxTip: 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.
2
To install required devDependencies such as typescript and @types/react in package.json:
# For all other package managers-Â npx expo install -- --save-dev typescript @types/react# For yarn-Â yarn add -D typescript @types/reactAlternatively, runnpx expo startcommand to installtypescriptand@types/reactdev dependencies.
3
A project's tsconfig.json should extend the expo/tsconfig.base by default. You can automatically generate a tsconfig.json file by running the command:
-Â npx expo customize tsconfig.jsonThe 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:
{
"compilerOptions": {
"strict": true
}
}
4
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:
{
"compilerOptions": {
"baseUrl": ".",
"paths": {
"@/*": ["src/*"]
}
}
}
Set tsconfigPaths to true to enable path aliases in the project's app config:
{
"expo": {
"experiments": {
"tsconfigPaths": true
}
}
}
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:
{
"expo": {
"experiments": {
"tsconfigPaths": false
}
}
}
When using path aliases, consider the following:
@expo/webpack-config.5
To enable absolute imports from a project's root directory, define compilerOptions.baseUrl the tsconfig.json file:
{
"compilerOptions": {
"baseUrl": "./"
}
}
For example, setting the above configuration allows importing Button component from the path src/components/Button:
import Button from 'src/components/Button';
Set tsconfigPaths to true to enable absolute imports in the project's app config:
{
"expo": {
"experiments": {
"tsconfigPaths": true
}
}
}
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.compilerOptions.baseUrl after modifying the tsconfig.json.@expo/webpack-config.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.
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.
# For all other package managers-Â npx expo install -- --save-dev ts-node# For yarn-Â yarn add -D ts-nodeUpdate metro.config.js to require metro.config.ts file:
require('ts-node/register');
module.exports = require('./metro.config.ts');
Update metro.config.ts file with your project's metro configuration:
import { getDefaultConfig } from 'expo/metro-config';
const config = getDefaultConfig(__dirname);
module.exports = config;
Install the @expo/webpack-config package.
require('ts-node/register');
module.exports = require('./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.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:
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;
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.
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.