Installing

Before you begin, make sure you have Node.js 18 or higher installed. Then, create a directory for your application and navigate into it.

mkdir myapp
cd myapp

Use the npm init command to create a package.json file for your application. For more information on how package.json works, see Specifics of npm’s package.json handling.

npm init

yarn init

pnpm init

bun init

This command prompts you for a number of things, such as the name and version of your application. For now, you can simply hit RETURN to accept the defaults for most of them, with the following exception:

entry point: (index.js)

Enter app.js, or whatever you want the name of the main file to be. If you want it to be index.js, hit RETURN to accept the suggested default file name.

Now, install Express in the myapp directory and save it in the dependencies list. For example:

npm install express

yarn add express

pnpm add express

bun add express

To install Express temporarily and not add it to the dependencies list:

npm install express --no-save

bun add express --no-save

TypeScript

Express is written in JavaScript and does not bundle its own type definitions. To use it with TypeScript, install TypeScript together with the community-maintained types for Express and Node.js (from DefinitelyTyped) as development dependencies:

npm install --save-dev typescript @types/express @types/node

yarn add --dev typescript @types/express @types/node

pnpm add --save-dev typescript @types/express @types/node

bun add --dev typescript @types/express @types/node

Add a tsconfig.json. These options mirror how Node.js runs TypeScript and make the compiler reject non-erasable syntax (such as enums, namespaces, and parameter properties) that Node cannot strip:

{
  "compilerOptions": {
    "target": "esnext",
    "module": "nodenext",
    "rewriteRelativeImportExtensions": true,
    "erasableSyntaxOnly": true,
    "verbatimModuleSyntax": true,
    "noEmit": true,
    "strict": true,
    "skipLibCheck": true
  }
}

Write your application in TypeScript, annotating the request and response objects:

import express, { type Express, type Request, type Response } from 'express';

const app: Express = express();

app.get('/', (req: Request, res: Response) => {
  res.send('Hello World!');
});

app.listen(3000);

You do not need to annotate everything. When you pass a handler directly to a route method or to app.use(), Express infers the types of req, res, and next, and it infers route parameters from the path, so req.params.id is a string in app.get('/users/:id', ...). Add explicit types only where TypeScript has no context to infer from: error-handling middleware, whose (err, req, res, next) signature is not inferred, and handlers you define separately from the route. In those cases, annotate the parameters or type the whole function as RequestHandler or ErrorRequestHandler.

Run the file directly with Node.js, which strips the TypeScript types and runs the result without a build step:

node src/app.ts