How to Validate Unique Emails with Mongoose

With Mongoose, you can prevent duplicates in your databases using validation. Validation is defined in the SchemaType and is a middleware. You can also create your own validation in the schema or you can use Mongooses's built in validation. To prevent duplicates, we recommend using the unique property as it tells Mongoose each document should have a unique value for a given path. It is a shorthand for creating a MongoDB unique index on, in this case, email.

If you wait for the index to be built, you can you Mongoose's promised based event, Model.init(), as shown below:

const User = mongoose.model('User', mongoose.Schema({
  email: { 
    type: String,
    required: true,
    match: /.+\@.+\..+/,
    unique: true
  }
}));
await User.create([
    { email: 'gmail@google.com' },
    { email: 'bill@microsoft.com' },
    { email: 'test@gmail.com' }
]);

await User.init();
try {
  await User.create({ email: 'gmail@google.com' });
} catch(error) {
  error.message; // 'E11000 duplicate key error...'
}

It is important to note that the unique property is not a validator.

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