Mongoose comes with several built-in validators. Some validators are present in all data types and some are exclusive for a data type. For example, a String field will have the min and max validators but a Boolean type will not.

Let's add some validations to our Team schema. Open the mongoose-connection.js file and apply the following changes:

...
const TeamSchema = new mongoose.Schema({
  name: {
    type: String,
    min: 3,
    max: 100,
    required: true,
    unique: true
  },
  ranking: {
    type: Number,
    min: 1
  },
  captain: {
    type: String,
    required: true
  },
  Trainer: {
    type: String,
    required: true
  },
  confederation: {
    type: String,
    required: true,
    uppercase: true
  }
})

Now, our schema looks more professional and will help us validate the data before it is persisted in MongoDB. Most of the validators are self-explanatory. As you might have noticed, when you want to apply validators, the syntax to declare a field changes a little bit; in this case, a JavaScript object should be passed to define the data type and validators. To find more information about validators, visit http://mongoosejs.com/docs/validation.html.