ExpressJS in a TypeScript class

Question

All ExpressJS and TypeScript examples I could find use

import * as express from "express";

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

However, I want to use the class approach:

import * as express from "express";

export class ServerApp {

    private app: express.Express = express();

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

Trying to access the use method on the private variable gives an argument type warning.

I want to use strong typing so private app: any will not work. How can I solve this problem, or is there a better approach?

artem · Accepted Answer · 2016-09-24 19:55:51Z

1

According to the latest express typings, the type for app is called Application, not Express. The following file test.ts compiles just fine

import * as express from "express";

export class ServerApp {

    private app: express.Application = express();

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

if you put it in an empty directory and do

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

it will work.

However, there is more than one way to install typings for express. If you don't need compatiblity with typescript < 2.0 (2.0 was released a few days ago), you can just

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

and again it will work. If you look at installed types-metadata.json for express-serve-static-core, you notice that it uses types-2.0 branch of DefinitelyTyped:

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

The third way to install is

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

this will take it from the main branch of DefinitelyTyped, which, as @Aphelion discovered, contains problematic commit that removes a number of use overloads, causing the error in question.

edited Sep 24, 2016 at 19:55

answered Sep 23, 2016 at 23:41

artem

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5 Comments

Myrtle Over a year ago

It indeed compiles correctly. For some reason however, my tool WebStorm gives this warning but gets its definitions from express-serve-static-core. Any Idea why it would prefer this over the normal definitions?

Myrtle Over a year ago

This might cause the problem:github.com/DefinitelyTyped/DefinitelyTyped/commit/…

artem Over a year ago

Yes you are right! Whatever I did probably used types-2.0 branch of DefinitelyTyped which does not contain that commit. I updated the answer. BTW I also use WebStorm, and it seems to me that it just uses whatever is installed in node_modules and typings.

Myrtle Over a year ago

Unfortunately the commit has been merged to the typings2.0 branche.

artem Over a year ago

I just checked again with npm install @types/express and it still works. Either it's not published on npm yet, or that commit is not really the problem.

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