MERN router.get 请求返回未定义

Question

So, I'm trying to use a get request to find the email of a user and display the information on screen. To do this, I set a local storage item with the user's email and am trying to reference this in my api call. However, on the back-end side of things, when I try and send the email through an axios call it doesn't make it to the back-end where I can do anything with it. I'm getting a status code 500 error along with this TypeError: Cannot read property 'then' of undefined .

This is my router.get function that's throwing the error

router.get("/user", function(req, res) {
  console.log("id hit");
  console.log(req.data);
  console.log(req.params.email);
  db.User
      .getUserByEmail(req.params.email)
      .then((dbModel) => res.json(dbModel))
      .catch((err) => res.status(422).json(err));
});

This is my getUserByEmail function

module.exports.getUserByEmail = function (email, callback) {
  console.log("getUserByEmail", email)
  var query = { email: email };
  console.log(query);
  User.findOne(query, callback);
};

This is my front-end API axios call

getUser: function(email) {
    console.log("API EMAIL: ",email);
    return axios.get("/api/users/user/", email);
  }

And this is my componentDidMount on the page I want to display the information on

 componentDidMount() {
        const userEmail = localStorage.getItem("userEmail");
        this.setState({
            email: userEmail
        }, () => {
            console.log(this.state.email);
            API.getUser(this.state.email)
            .then(data => {
                this.setState({
                    firstName: data.firstName,
                    lastName: data.lastName,
                })
            })
        })
    }

I'm able to reference the email on the front-end side of things, but once it gets to the back-end, everything's undefined. Any help is appreciated.

Answer 1

module.exports.getUserByEmail = function (email, callback) {
  console.log("getUserByEmail", email)
  var query = { email: email };
  console.log(query);
  User.findOne(query, callback);
};

This function doesn't return anything you need to return something from it.

you could do

return user.findOne(query, callback);

as long as user.findOne returns something and if its mongoose or mongo its probably a proimse.

Also you need the route to be

router.get("/user/:email", function(req, res)