> For the complete documentation index, see [llms.txt](https://structure.js.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://structure.js.org/validation/string-validations.md).

# String validations

* `required`: can't be undefined (default: `false`)
* `empty`: accepts empty string (default: `false`)
* `equal`: **\*** equal to passed value
* `minLength`: can't be shorter than passed value
* `maxLength`: can't be longer than passed value
* `exactLength`: length must be exactly the passed value
* `regex`: matches the passed regex
* `alphanumeric`: composed only by alphabetical and numeric characters
* `lowerCase`: all characters must be lower cased
* `upperCase`: all characters must be upper cased
* `email`: is a valid email (default: `false`)
* `nullable`: accepts null (default: `false`)
* `guid`: is a valid guid. You can pass a boolean or the [options object accepted by Joi](https://hapi.dev/module/joi/api/?v=16.1.8#stringguid---aliases-uuid) (default: `false`)

```javascript
const User = attributes({
  id: {
    type: String,
    guid: true,
  },
  token: {
    type: String,
    guid: {
      version: ['uuidv4'],
    },
  },
  initials: {
    type: String,
    upperCase: true,
    maxLength: 4,
  },
  gender: {
    type: String,
    nullable: true,
  },
  password: String,
  passwordConfirmation: {
    type: String,
    equal: { attr: 'password' },
  },
  greet: {
    type: String,
    required: true,
    equal: ['Mr', 'Ms', 'Mrs', 'Miss', { attr: 'greetDesc' }],
  },
  greetDesc: String,
})(
  class User {
    getFullGreet() {
      return `${this.greet} ${this.initials}`;
    }
  }
);
```