# Getting started
Type-R is the modern JS data framework to manage complex domain and UI application state. Features:
- _It's mapped to JSON by default_. The mapping can handle sophisticated scenarios with nested JSON and relations by id, and can be easily customized for every particular attribute or class.
- _All changes are observable_, happens in the scope of transactions, and there's the fine-grained change events system.
- _Validation_ is performed on the first access to the validation error and never happens twice for unchanged data.
- _Everything is typed at run-time_ and is protected from improper updates. The shape of generated JSON and data classes is guaranteed to match the definitions.
- It still looks like regular JS classes and is freaking fast. Type-R data structures are about 10 times faster than Backbone models and collections.
Data layer is defined as a superposition of three kinds of building blocks:
- *Record* classes with typed attributes.
- Ordered *collections* of records.
- *Stores* are records with a set of collections in its attributes used to resolve id-references in JSON.
- *IOEndpoints* is an entity encapsulating I/O transport which represent the persistent collection of records.
Type-R is completely unopinionated on the client-server transport protocol and the view layer technology. It's your perfect M and VM in modern MVVM or MVC architecture.
```javascript
import { define, Record } from 'type-r'
// Define email attribute type with encapsulated validation check.
const Email = String.has.check( x => x! || x.indexOf( '@' ) >= 0, 'Invalid email' );
@define class User extends Record {
static attributes = {
name : String.isRequired, // should not be empty for the record to be valid.
email : Email.isRequired
}
}
@define class Message extends Record {
static attributes = {
created : Date // = new Date()
author : User, // aggregated User record.
to : User.Collection, // aggregating collection of users
subject : '',
body : ''
}
}
const msg = new Message();
assert( !msg.isValid() ); // Is not valid because msg.author has empty attributes
// Listen for the changes in aggregation tree...
msg.on( 'change', () => console.log( 'change!!!' ) );
msg.transaction( () => { // Prepare to make the sequence of changes on msg
msg.author.name = 'John Dee'; // No 'change' event yet as we're in the transaction.
msg.author.email = 'dee@void.com';
assert( msg.isValid() ); // Now msg is valid as all of its attributes are valid.
}); // Got single 'change!!!' message in the console.
```
## [Documentation](https://volijs.github.io/Type-R/)
## Installation and requirements
Is packed as UMD and ES6 module. No peer dependencies are required.
`npm install type-r --save-dev`