TypeScript icon, indicating that this package has built-in type declarations

    2.1.0-beta.0 • Public • Published

    NestedTypes 2.0 is BackboneJS compatibility layer for the Type-R data framework. Type-R is Model/Collection core written from the scratch with the TypeScript and has no side dependencies.

    NestedTypes adds support for REST (standard BackboneJS API), Underscore methods, and Backbone 1.1 classes. In the next versions Type-R will support configurable I/O adapters ( making it trivial to attach the custom I/O transport. Backbone-compatible REST functionality will be available via plugin.

    If you're upgrading from the version 1.3, there are compatibility issues. Mostly due to the fact that the Type-R and NestedTypes 2.0 is built around the concept of aggregation trees. NestedTypes 1.3 code won't work without refactoring.


    Post-backbone data framework. 10 times faster, first-class support for nested models and collections and relations by id.

    • ES6 classes support.
    • Deeply observable changes.
    • First-class support for aggregation and relations by id.
    • Attribute type annotations and dynamic type safety.
    • More than 10 times faster than BackboneJS and 2-4 times faster than NestedTypes 1.3 in all browsers.

    Installation & Requirements

    All modern JS engines are supported (IE10+, Safari, Firefox, Edge, Chrome, nodejs). May work in IE9 but not tested.

    npm install nestedtypes

    underscore and jquery are hard dependencies.

    For lighter framework version without dependencies and Backbone compatibility shim check out Type-R.

    Quick API Reference

    Central concept in NestedTypes is Record type, which is the JS class with following capabilities:

    • Class members are deeply observable.
    • It is serializable to JSON by default.
    • Class members are typed and their changes are guardered with run-time type checks.

    Model is the Record subclass representing REST API endpoint. Models, records, and their collections are used as building blocks to describe both application's UI state and its data layer.

    Record definition looks like normal ES6 class definition, but it's mandatory to declare attributes. It looks like this:

    import { define, Record } from 'nestedtypes'
    @define // <- decorator to perform class transformation
    class User extends Model {
        urlRoot : '/api/users',
        static attributes = { // <- attributes declaration
            name : '', // <- can be either default value
            email : String, // <- or any JS type constructor
            isActive : true,
            lastLogin : Date.value( null ) // <- or both
    const user = new User({ id : 5 }); // <- constructor takes optional attributes hash as an argument
    user.fetch().done( () => { // GET /api/users/5 = 'John';; // PUT /api/users/5

    Record's Attributes Type Annotations Basics

    All record's attributes must be declared with static attributes = { [ attrName ] : TypeAnnotation } member. Type annotation can be one of the following:

    • attrName : Constructor. Such as attrName : Date.
    • attrName : Constructor.value( defaultValue ). Such as lastLogin : Date.value( null ).
    • attrName : defaultValue. In this case, attribute type will be inferred from the value, so isActive : true has the same effect as isActive : Boolean.value( true ).

    Record attributes can be accessed directly, like = x. When attribute is assigned, the type of the the value is checked and being converted to the declared type with its constructor invocation if it's necessary.

    For the assignments like user.isActive = x, where isActive is declared as Boolean

    • it is assigned as is if x is null or boolean.
    • for primitive types, it's converted with plain constructor invokation like Boolean( x ).
    • For non-primitives convertion will invoke constructor with new, like new Date( x ).

    If it's impossible to convert the value it may be assigned with NaN or Invalid Date (or depending on the type update will be rejected), and there will be an error in the console.

    Therefore, it's guaranteed that Record attributes always have declared type.


    Every model has corresponding Collection type declared implicitly. Collections implements Backbone Collection API.

    var users = new User.Collection();
    users.fetch().done( () => {
        console.log( users.length );

    When Record is extended, its collection is extended too. The creation of implicit Colleciton type is equivalent to this:

    class Users extends Record.Collection {} 
    class User extends Record {
        static Collection = Users;
        // ...

    You can use this pattern when you need to add custom members to the record's collection.

    Nested Records and Collections

    Nested records and collections are declared with mentioning constructor in attribute type annotation. All changes in nested objects are deeply observable; any change in children will cause change events in a parent.

    Records and collections emiting the standard set of Backbone events, with following differences:

    • Collections does not bubble change:[attribute] event from the model by default (change event is bubbled); event bubbling needs to be enabled for every particular event with static itemEvents = { 'change:attr1' : true, ... } declaration.
    • Collections have changes event which is semantically similar to the model's change.


    Record's change event (and collection's changes event) are transactional. Whatever some changes are made as the reaction on any of change event, it won't cause additional change event for the owner.

    Also, you can explicitly group the sequence of changes to the single transaction:

        some.record.transaction( record => {
            record.a = 1;
            record.b = 2;
        }); // some.record will emit single 'change' event if there was any changes.
        // Execute collection.each in the scope of transaction.
        todoCollection.updateEach( item => item.done = true ); // One 'changes' event will be emitted. 


    Record can aggregate other records and collections in its attributes.

    class Team extends Record {
        static attributes = {
            members : User.Collection
            leader : User
    const team = new Team();
    team.members.add( new User({ name : 'John' }) );

    Aggregated members are:

    • serialized as nested JSON.
    • following operations recursively when the operation happens to its owner.

    Aggregated members forms the tree of exclusive ownership. The same record or collection instance cannot be aggregated in two places at the same time, and this rule is checked and enforced.

    Shared nested objects

    Records may have nested members which belongs to different ownership trees. Special type annotations are required to mark attribute as shared.

    • RecordType.shared or CollectionType.shared. Reference to collection or record which may be aggregated somewhere else. null by default.
    • CollectionType.Refs constructor. Collection of records which may be aggregated somewhere else. Defaults to empty collection.

    CollectionType.Refs is an equivalent to CollectionType.shared.value( [] ) when used as attribute type annotation.

    Shared types are:

    • not a part of record's ownership tree.
    • not serialized.
    • Not a subject of recursive operations. They are empty by default, not cloned, not validated, and not disposed when the corresponding operation applied to the parent.

    In all other aspects, they are indistinguishable from aggregated records and collections.

    class Team extends Record {
        static attributes = {
            members : User.Collection.Refs
            leader : User.shared

    Relationship by id

    It's possible to create serializable reference to the shared object which is represented in JSON as a record's id (or array of ids). Special type annotation is required to point out the master collection which will be used to resolve ids to the records.

    • RecordType.from( masterCollection ) represents an id reference to the model.
    • CollectionType.subsetOf( masterCollection ) represents the collection of models id references.

    id-reference types behaves as shared types, but:

    • they are serializable as an object id (or array of ids for collections).
    • they are not observable (internal changes do not trigger change events on the record).

    masterCollection reference may be either:

    • direct reference to the globally available collection.
    • function returning the reference to the collection.
    • string, which is the symbolic reference to collection (dot-separated path to the collection taken relative to the record's this).
    class Team extends Record {
        static attributes = {
            members : User.Collection,
            leader : User.from( 'members' ) // <- leader is serializable reference to the record from members collection.  


    ^ symbol in symbolic reference represents getOwner() call and returns the record owner. Collections are skipped.

    Following example expects that Team record will be aggregated (alone or in a collection) together with users collection.

    class Team extends Record {
        static attributes = {
            members : User.Collection.subsetOf( '^users' ),
            leader : User.from( 'members' )  

    Tilda-References and Stores

    Symbolic reference staring with ~ is resolved relative to the record called store, which is located with record.getStore() method. For instance, reference ~users will be resolved as this.getStore().users.

    getStore() uses following store location algorithm:

    1. It traverse an ownership tree upwards and return the first Store model it has found.
    2. If none of the record's owners is the Store, it returns global store from

    Store is the subclass of the Record and behaves as a regular Record. Therefore, resolution of id references depends on the context and you may have as many stores as you like.

    Following example expects that there's users collection in some upper record which is inherited from Store, or (if there are none) in the global store:

    class Team extends Record {
        static attributes = {
            members : User.Collection.subsetOf( '~users' ),
            leader : User.from( 'members' )  

    Attribute has-annotations

    It's possible to control different aspects of record's attribute behavior through additional metadata. All of them starts with a keyword .has added to the constructor type.

    Object describing an attribute is called metatype. Operations on metatypes are immutable (returns new metatype), and can be chained.

    // Declare Month metatype.
    const Month = Number.value( 1 ).has.check( x => x > 0 && x <= 12 );

    attribute : Type.has.toJSON( false | ( x, name ) => json )

    Override default serializer for the attribute. false option will exclude attribute from serialization.

    attribute : Type.has.parse( ( json, name ) => data )

    Override default JSON parser for the attribute.

    attribute : Type.has.get( ( value, name ) => value )

    Get hook which may transform attribute value on read. Get hooks can be chained.

    attribute : Type.has.set( ( value, name ) => value )

    Set hook which may transform attribute value before it's assigned. Set hooks can be chained.

    attribute : RecordOrCollectionType.has.changeEvents( false )

    When nested attribute is changed, don't mark the owner as changed.

    attribute :{ [ event ] : handler | handlerName })

    Listen to the specified events from the attribute. handler can be either function or the name of the record's method.

    attribute : Type.has.check( x => boolean, errorMsg? : any )

    Attach check to the attribute. Checks can be chained. Attribute is valid whenever check function returns truthy value.

    errorMessage is optional.

    attribute : Type.isRequired

    Similar to Type.has.check( x => x, 'Required' ).


    Validation is performed recursively on ownership tree. Record and collection shares the same validation API.


    Override it to add custom record-level validation. Method shoudl return truthy value in case of validation error.

    For attribute level checks see Type.has.check annotation.

    record.isValid() : boolean

    Checks whenever record is valid.


    Return validation error object or null if there are no errors.


    npm i nestedtypes-next

    DownloadsWeekly Downloads






    Last publish


    • avatar