Node.JS one of three same-structured paths is not working

I am pretty new to Node.js and I am currently building a backend api for a project. I´ve got 3 routes in my app. societies, users and emails.

   //module for email stuff
   emailsModule = require('./api/routes/emails')(connection);
   const emailsRoutes = emailsModule.router;
   app.use('/emails', emailsRoutes);
   
   //module for societies
   societyModule = require('./api/routes/societies')(connection);
   const societyRoutes = societyModule.router;
   app.use('/societies', societyRoutes);

   //module for users
   usersModule = require('./api/routes/users')(connection);
   const usersRoutes = usersModule.router;
   app.use('/users', usersRoutes);

The societies and emails modules are working, but the emails module is not working.
I just cannot figure out why it isn´t working, I have tried various things but the emails module just doesn´t work. Postman output says "Cannot GET /emails/.
This is my module.exports function:

module.exports = function(connection) {
    module.connection = connection;
    sql = connection;
    module.router = router;
    console.log("sacramento");    //test output
    return module;
}

An example route is

router.get("/:email"), (req, res) => {
    var credentialCheck = new sql.Request();
    credentialCheck.input("email", sql.VarChar, req.query.email);
    credentialCheck.input("passwort", sql.VarChar, req.body.password);
    credentialCheck.execute("checkSocietyCredentials",
    (er, result) => {
        if ( er ) {
            res.status(200).send({
                error:er
            });
        }
        else {
            res.status(200).send(
               {
                   isEmailValid    : result.recordsets[0][0],
                   isPasswordValid : result.recordsets[0][1]
               } 
            );
        }
    });
}

It could be just a little stupidity error like // in a path.
The URL i am using for this module is http://localhost:3000/emails/?email=example@gmail.com. I I would be really thankful if someone would find the error in my script.

I see multiple issues that will need to be corrected.

This syntax is wrong:

router.get("/:email"), (req, res) => {

It should be

router.get("/:email", (req, res) => { 

and then you will have to add ) at the end of the function's code.

You were essentially just defining a route for:

router.get("/:email")

with no route handler at all. And, then you were declaring an arrow function, but not doing anything with it. Assuming this actually parsed in the interpreter, you just got unlucky in that a typo that messed up your code just happened to compile and not report an error (happens sometimes in all languages, more often in a non-typed language).

Also, with:

app.use('/emails', emailsRoutes)

and

router.get("/:email")

The route you request should be /emails/someEmail where someEmail is whatever you want the :email parameter to be. If that's an actual email address, it will have to be properly URL encoded.

And, in that /:email route handler, you are referring to req.body.password. That will not work. req.body is empty for a GET request. That is only used for a POST or PUT request and will only be filled in if you use the right middleware o read and parse the body into req.body.

If you are intending to pass both an email and a password to this route, then it should probably be a POST request and both email and password should arrive in the body.

This is because you defined an email route parameter as a sub route of /emails.

Therefore the expected url should be something like this http://localhost:3000/emails/example@gmail.com.

You have two options.

1. change the route definition to router.get("/", ...)
2. leave your route definition as router.get("/:email", ...), change the url to be like the example above and access the email like so req.params.email

I guess you are using express. Check the routing documentation here for more information regarding route parameters.