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Extend Express's Request Object with Typescript Declaration Merging.

Kwabena Bio Berko on January 29, 2020

Express has been my go to server side node web framework for the past few years. Its fast, unopinionated and so easy to get up and running. I reall...

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aashishClikFin • Jan 13 '21 • Edited

First of all thanks a lot for your post, I finally resolved the problem I faced since the last 3 months.

Just would like to add one more bit, since I was using passport alongside passport-jwt hence your solution didn't exactly work for me.

Here is what I used in the index.d.ts file

declare module 'express-serve-static-core' {
export interface Request {
user?: yourCustomType;
}
}

It might help someone else as well, but thanks a lot for guiding me in the right direction.

Jinendra Jain • Apr 10 '22

Thanks Bro

playground • Feb 9 '22

Great article, thanks for sharing. Good to know there is another way of doing things.
I have been doing it the inverse by extending Request

For example:
export interface IRequest extends Request {
type: string;
sensorId: string;
timestamp: ITime;
}

in the server.ts
...
app.get("/test", (req: IRequest, res: IResponse) => {
...
})

Adil • Nov 19 '20 • Edited

Thank you, it helped. But as far as I understood, it adds currentUser field to all Requests? What if I want it to be present only in the current file and not declared in the other files where I use Request?

Luca S. Martins • Apr 1 '22

You could declare currentUser as optional and use it when needed

Gabriel • Jun 25 '21

NOTE that you have to add typeRoots inside compilerOptions in the tsconfig.json file.

Vitalii • Mar 23 '21

Nice article! You saved my day 😎👍

I see a lot of libraries using this approach.

But It looks a bit strange for me. Just imagine that you have a lot of middleware that attaches something to the request object. In the end, you have a bloated interface and you lose the power of TypeScript because you don't know which middlewares were executed before handler/controller. So you don't know if the required data was attached and need to double-check if it's there 🤷‍♂️.

Peter Kitonga • Aug 13 '21 • Edited

If anyone is still having errors with this, don't forget to import Express at the top of your file.

import { Express } from 'express'

For some reason, I couldn't get it to work without the import

Luca S. Martins • Apr 1 '22

Thanks! Same problem here.

Nguyễn Công Trọng • Feb 2 '23

Thanks!

Pendar • Dec 10 '20

This was awesome! I was missing the step with having to create the same folder path structure and adding the "typeRoots"

Qi Mu • Apr 24 '20

Thank you so much!!!

Kwabena Bio Berko • May 2 '20

You're welcome. 😊

Dan Maia • Sep 11 '21

The best article about that I've found today in the Internet.

Diego CS • Feb 24 '21

Thanks!!!!!!!! I was looking for information, but all that I found was not useful, but your explanation goes straight to the point. Than you very much.

TJSarkka • Mar 8 '20

Thank you! I spent the last hours scratching my head and trying different combinations of config files and .d.ts files provided in other solutions.. and this was the only one that worked for me for both ts-node and tsc. :)

Kwabena Bio Berko • May 2 '20

You're welcome.
Glad to be of help.

Mark Tsai • May 2 '20 • Edited

Similar methods to define Request types can also be found in the following libraries:

I also spent so much time resolving this issue, thank you for your article!

Kwabena Bio Berko • May 2 '20

You're welcome
Really glad you found it useful.

damjuve • Mar 5 '21

Hello,

Thanks for this very usefull tips.
I still have a question about exporting this.
I would like to extend express Request with UserModel, exactly like you did. But I am doing it in a homemade node module.
Then I install this node module in a node project and I don't have access to the extended request. How can i do this ?

George C. Norris • Sep 17 '20

Getting a Augmentations for the global scope can only be directly nested in external modules or ambient module declarations. ??

Simon Texson • Nov 25 • Edited

Thanks for this article.

I had to import the Express and Request objects into the index.d.ts file like so:

import Express, {Request} from 'express'
import {UserModel} from 'path/to/user/model'

declare global {
    namespace Express {
        interface Request {
            currentUser: UserModel;
        }
    }
}

Hope this helps someone else.

Comment deleted

Kwabena Bio Berko • Oct 23 '22

Hi, @wardvisual, thanks for reading.
The node_modules folder was not modified in this article. We created a new file, @types > express > index.d.ts in the root of our project, not in node_modules 🙂

Hassan • Jan 25 '23 • Edited

Thanks alot for the clear explanation,
i've used your solution and it works berfictly with node ./dist/server.js and the compilation as well, however every time i use tsc watch i got the following error

error TS2339: Property 'currentUser' does not exist on type 'Request<ParamsDictionary, any, any, ParsedQs, Record<string, any>>.

riejoc16 • Aug 27 '20

Oh wow! I was stuck for a while now trying to achieve exactly that. I couldn't find what I had done wrong. Only with this post I was able to get it done, thanks!

Kwabena Bio Berko • Aug 29 '20

You're welcome. 😄

terabytes • Mar 2 '20

VS code doesn't show error in editor but during compilation i get:
currentUser does not exist on type 'Request'.
Its Ts error.

Mehmet N Yarar • Jul 9 '20

same here. not only that, testing (jest/ts-jest) also fails unless I do:

declare module 'express' {
  export interface Request {
    i18n: import('i18next').i18n
    language: string
  }
}

Beadle • Feb 11 '22

I am having the same issue. Did you every find a fix for this?

Asgamboa12 • Oct 24 '20

Thank you very much, this problem was killing me and I could not find a way to solve it until I saw your post, thank you very much !!!

Sakari Ellonen • Dec 21 '20

I created an account here just to say thank you, this was such a nice solution that a typescript newbie like me would not have come up on my own.

Kwabena Bio Berko • Jan 19 '21

I'm really glad you found it useful.

Rene Maldonado Fimbres • May 16 '20

Bro, have been having problems with this for 2 days.

Thanks for the info, I was missing the @ sign .

Kwabena Bio Berko • May 18 '20

You're welcome.

Ioannis • Nov 29 '20 • Edited

Could you add a GitHub link please. It does not work for me as well.

Kwabena Bio Berko • Oct 23 '22

github.com/KwabenBerko/node-backen...

jpolstre • Sep 23 '20 • Edited

Thanks, in my case work whitout: declare global {

George C. Norris • Sep 17 '20

I've tried SOO many variations to make this work, and NOTHING seems to work. 🤷🏻‍♂️

saurav kumar bhagat • May 18 '21

What if we directly extends the Request interface like:
export interface CustomReq extends Request{ currentUser: User }
and use this instead?

Kwabena Bio Berko • Oct 23 '22

This works as well 🙂

Anderson Luis Silva • Aug 8 '20

Thank you very much!
Very well explained.

Kwabena Bio Berko • Aug 10 '20

Thank you. 😊

Mourad EL CADI • Feb 16 '22

you're great)

tukuyoma • May 7 '21

thanks ...this helped alot