@types/express 4.17.21

The @types/express is an NPM package providing TypeScript type definitions specifically for the Express.js framework. In simpler terms, it's support for Express.js when working with TypeScript. It offers TypeScript developers rich development-time feedback which enhances code accuracy by providing static type checking and autocompletion.

To use the @types/express package in your project, you first need to install it using the Node Package Manager (NPM). The following is a simple example of how to use the @types/express package in your application.

Install the package:

npm install --save @types/express

After installation, whenever you import from the Express module, the TypeScript compiler will use the type definitions from the @types/express package.

import express, { Request, Response } from 'express';
const app = express();

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

In the above code example, 'Request' and 'Response' are TypeScript type definitions provided by the @types/express package.

The @types/express package is part of the DefinitelyTyped project, thus the official documentation is hosted on their Github repository. You can access the documentation from this URL: Definitely Typed. For a more specific location, all type definition files including the Express ones are located in the types directory. However, as a TypeScript type definition package, the @types/express does not provide extensive documentation like software libraries normally do. You'd use it more as a helper to other main libraries or frameworks (Express.js, in this case) rather than a standalone library. Hence, understanding and knowledge of Express.js itself is essential.