Implementing ExpressJS functionality within a TypeScript class

Searching through numerous examples of ExpressJS and TypeScript, I noticed they all follow a similar pattern:

import * as express from "express";

let app = express();
app.use("/", express.static("/"));

However, my preference is to employ the class approach instead:

import * as express from "express";

export class ServerApp {

    private app: express.Express = express();

    public configure {
        this.app.use('/', express.static("/");
    }
}

Encountering an argument type warning when trying to access the use method on the private variable was not ideal.

I strive for strong typing, making private app: any an inadequate solution. Is there a way to address this issue effectively, or perhaps a superior alternative exist?

Answer №1

As per the latest express typings update, the type for the app is now referred to as Application instead of Express. The code snippet below in test.ts compiles without any issues

import * as express from "express";

export class ServerApp {

    private app: express.Application = express();

    public configure() {
        this.app.use('/', express.static("/"));
    }
}

If you place it in a new directory and execute

npm install typescript
npm install typings
./node_modules/.bin/typings install -G dt~node
./node_modules/.bin/typings install express
./node_modules/.bin/tsc test.ts typings/index.d.ts

everything will function correctly.

There are alternative ways to install typings for express. If compatibility with typescript < 2.0 (which was recently released) is not required, simply run

npm install typescript
npm install @types/express
./node_modules/.bin/tsc test.ts

and the code will still work. By examining the installed types-metadata.json for express-serve-static-core, you can see that it utilizes the types-2.0 branch of DefinitelyTyped:

"sourceRepoURL": "https://www.github.com/DefinitelyTyped/DefinitelyTyped",
"sourceBranch": "types-2.0",

The third method of installation involves

../node_modules/.bin/typings install -G dt~express

this will retrieve it from the main branch of DefinitelyTyped. However, it's worth noting that this branch contains a problematic commit mentioned by @Aphelion, which removes certain use overloads and may result in the encountered error.

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