How to get the email of any user in Firebase based on user id?

Question

I need to get a user object, specifically the user email, I will have the user id in this format:

simplelogin:6

So I need to write a function something like this:

getUserEmail('simplelogin:6')

Is that possible?

Answer 1

It is possible with Admin SDK

Admin SDK cannot be used on client, only in Firebase Cloud Functions which you can then call from client. You will be provided with these promises: (it's really easy to set a cloud function up.)

admin.auth().getUser(uid) admin.auth().getUserByEmail(email) admin.auth().getUserByPhoneNumber(phoneNumber) 

See here https://firebase.google.com/docs/auth/admin/manage-users#retrieve_user_data

---

In short, this is what you are looking for

admin.auth().getUser(data.uid)   .then(userRecord => resolve(userRecord.toJSON().email))   .catch(error => reject({status: 'error', code: 500, error})) 

full snippet

In the code below, I first verify that the user who calls this function is authorized to display such sensitive information about anybody by checking if his uid is under the node userRights/admin.

export const getUser = functions.https.onCall((data, context) => {   if (!context.auth) return {status: 'error', code: 401, message: 'Not signed in'}    return new Promise((resolve, reject) => {     // verify user's rights     admin.database().ref('userRights/admin').child(context.auth.uid).once('value', snapshot => {       if (snapshot.val() === true) {         // query user data         admin.auth().getUser(data.uid)           .then(userRecord => {             resolve(userRecord.toJSON()) // WARNING! Filter the json first, it contains password hash!           })           .catch(error => {             console.error('Error fetching user data:', error)             reject({status: 'error', code: 500, error})           })       } else {         reject({status: 'error', code: 403, message: 'Forbidden'})       }     })   }) })  

BTW, read about difference between onCall() and onRequest() here.