Using Express with Typescript to include values in router.param

Question

Using Express with Typescript to include values in router.param

Express 4.x API provides an example for utilizing Router.param:

router.param('user', function (req, res, next, id) {
  // Attempt to retrieve user details from the User model and attach it to the request object
  User.find(id, function (err, user) {
    if (err) {
      next(err)
    } else if (user) {
      req.user = user
      next()
    } else {
      next(new Error('Failed to load user'))
    }
  })
})

What is the most effective approach to make this work with TypeScript? The statement req.user = user will not function as expected in this scenario, as the express.Request object does not contain a user property.

Once that hurdle is overcome, how can you implement it in a subsequent router.get call?

typescript express

Answer 1

Answer №1

To start, make a fresh file named awesome.d.ts.

You have the ability to include new properties to the Express.Request interface in this manner:

declare namespace Express {
    export interface Request {
        myCustomProperty?: string
    }
}

This will enable you to perform actions such as the following:

app.param('user', function(req: Request, res: Response, next: NextFunction, id: string) {
    User.find(id, function(err, user) {
        if (err) {
            next(err);
        } else if (user) {
            req.user = user;
            next();
        } else {
            next(new Error('failed to load user'));
        }
    });
});

If you wish to restrict the addition of the property to every request, you can achieve this by establishing a new interface that expands upon the Request interface. Then you can utilize the updated interface within the express callback function like so:

interface CoolerRequest extends Request {
  user?: string;
}

app.param('user', function(req: CoolerRequest , res: Response, next: NextFunction, id: string) {
    // Now, req.user is only accessible here
});

Answer 2

To start, make a fresh file named awesome.d.ts.

You have the ability to include new properties to the Express.Request interface in this manner:

declare namespace Express {
    export interface Request {
        myCustomProperty?: string
    }
}

This will enable you to perform actions such as the following:

app.param('user', function(req: Request, res: Response, next: NextFunction, id: string) {
    User.find(id, function(err, user) {
        if (err) {
            next(err);
        } else if (user) {
            req.user = user;
            next();
        } else {
            next(new Error('failed to load user'));
        }
    });
});

If you wish to restrict the addition of the property to every request, you can achieve this by establishing a new interface that expands upon the Request interface. Then you can utilize the updated interface within the express callback function like so:

interface CoolerRequest extends Request {
  user?: string;
}

app.param('user', function(req: CoolerRequest , res: Response, next: NextFunction, id: string) {
    // Now, req.user is only accessible here
});

Using Express with Typescript to include values in router.param

Answer №1

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