How to write case statement in mongoDb using mongoose

Here I am using mongoose for my Mean application which consists of nodejs, expressjs and angularjs.

My problem here is I need to use different find conditions and according send the error message or data

Now I am using as below

User.findOne({ Email: req.body.Email }, (err, user) => {
                if (err) { return done(err); }
                if (!user) {
                    return res.json("Account with that email address does not exist.");
                }

mongoose schema

const userSchema = new mongoose.Schema({
    FirstName: String,
    LastName: String,
    Email: { type: String, unique: true },
    UserName: String,
    Password: String,
    PhoneNumber: String,
    EmailVerified : Boolean,
    AdminApproved : Boolean   
}, { versionKey: false });

but now I had fields like email verified and adminapproved.

In Ms-Sql i used case statement like

1. where (Email not present) then show Email not exist
2. where (Email present and not email verified ) then show please verify email
3. where (Email present, Email verified and not adminapproved) then show wait for admin process

Can anyone help me in mongoDB using mongoose how to achieve the same operation.

via charan tej