Tried to use data outside from function (firebase) [duplicate]

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• How do I return the response from an Observable/http/async call in angular2? 4 answers

i tried to use the data outside my function but it not works, token is everytime undefined. Can anyone help me ?

    getUserToken(id) {
    let token;
     firebase.database().ref("Users/"+id).child("token").on("value",(snapshot)=> {
        token = snapshot.val();

    });
    console.log(token);
    //return user[0].id.token;
}