What is the proper way to validate email uniqueness with mongoose?

Question

I cannot find a proper way to provide validation for email uniqueness in mongoose. Nothing I have found actually works. I was thinking to use Schema.pre, but how would I go about writing the code for that if that is the case? The Mongoose documentation is very poor and does not describe how or what pre does.

I would appreciate it if somebody could tell me how this is normally done or point me in the right direction. I don't understand why something so simple has no simple solution in mongoose...

Answer 1

You could use a custom validator:

var userSchema = new Schema({
  email: {
    type: String,
    validate: {
      validator: async function(email) {
        const user = await this.constructor.findOne({ email });
        if(user) {
          if(this.id === user.id) {
            return true;
          }
          return false;
        }
        return true;
      },
      message: props => 'The specified email address is already in use.'
    },
    required: [true, 'User email required']
  }
  // ...
});