CKEditor Ecosystem Documentation
Search
Home/CKEditor 5/API
Class

Collection (utils)

@ckeditor/ckeditor5-utils/src/collection

class
See source

Collections are ordered sets of objects. Items in the collection can be retrieved by their indexes in the collection (like in an array) or by their ids.

If an object without an id property is being added to the collection, the id property will be generated automatically. Note that the automatically generated id is unique only within this single collection instance.

By default an item in the collection is identified by its id property. The name of the identifier can be configured through the constructor of the collection.

Filtering

Type parameters

  • T : extends Record<string, any>

    The type of the collection element.

Properties

  • readonly

    first : null | T

    See source

    Returns the first item from the collection or null when collection is empty.

  • readonly

    last : null | T

    See source

    Returns the last item from the collection or null when collection is empty.

  • readonly

    length : number

    See source

    The number of items available in the collection.

  • private

    _bindToCollection : null | Collection<any> | undefined

    See source

    A collection instance this collection is bound to as a result of calling bindTo method.

  • private readonly

    _bindToExternalToInternalMap : WeakMap<any, T>

    See source

    A helper mapping external items of a bound collection (bindTo) and actual items of this collection. It provides information necessary to properly remove items bound to another collection.

    See _bindToInternalToExternalMap.

  • private readonly

    _bindToInternalToExternalMap : WeakMap<T, any>

    See source

    A helper mapping items of this collection to external items of a bound collection (bindTo). It provides information necessary to manage the bindings, e.g. to avoid loops in two–way bindings.

    See _bindToExternalToInternalMap.

  • private readonly

    _idProperty : string

    See source

    The name of the property which is considered to identify an item.

  • private readonly

    _itemMap : Map<string, T>

    See source

    The internal map of items in the collection.

  • private readonly

    _items : Array<T>

    See source

    The internal list of items in the collection.

  • private

    _skippedIndexesFromExternal : Array<number>

    See source

    Stores indexes of skipped items from bound external collection.

Methods

  • constructor( initialItems, [ options ] = { [options.idProperty] } )

    See source

    Creates a new Collection instance with specified initial items.

    const collection = new Collection<{ id: string }>( [ { id: 'John' }, { id: 'Mike' } ] );

console.log( collection.get( 0 ) ); // -> { id: 'John' }
console.log( collection.get( 1 ) ); // -> { id: 'Mike' }
console.log( collection.get( 'Mike' ) ); // -> { id: 'Mike' }

    You can always pass a configuration object as the last argument of the constructor:

    const nonEmptyCollection = new Collection<{ name: string }>( [ { name: 'John' } ], { idProperty: 'name' } );
nonEmptyCollection.add( { name: 'George' } );
console.log( collection.get( 'George' ) ); // -> { name: 'George' }
console.log( collection.get( 'John' ) ); // -> { name: 'John' }

    Type parameters

    T : extends Record<string, any>

    Parameters

    initialItems : Iterable<T>

    The initial items of the collection.

    [ options ] : object

    The options object.

    Properties
    [ options.idProperty ] : string

    The name of the property which is used to identify an item. Items that do not have such a property will be assigned one when added to the collection.

  • constructor( [ options ] = { [options.idProperty] } )

    See source

    Creates a new Collection instance.

    You can pass a configuration object as the argument of the constructor:

    const emptyCollection = new Collection<{ name: string }>( { idProperty: 'name' } );
emptyCollection.add( { name: 'John' } );
console.log( collection.get( 'John' ) ); // -> { name: 'John' }

    The collection is empty by default. You can add new items using the add method:

    const collection = new Collection<{ id: string }>();

collection.add( { id: 'John' } );
console.log( collection.get( 0 ) ); // -> { id: 'John' }

    Type parameters

    T : extends Record<string, any>

    Parameters

    [ options ] : object

    The options object.

    Properties
    [ options.idProperty ] : string

    The name of the property which is used to identify an item. Items that do not have such a property will be assigned one when added to the collection.

  • Symbol.iterator() → Iterator<T, any, undefined>

    See source

    Iterable interface.

    Returns

    Iterator<T, any, undefined>

  • add( item, [ index ] ) → Collection<T>

    See source

    Adds an item into the collection.

    If the item does not have an id, then it will be automatically generated and set on the item.

    Parameters

    item : T
    [ index ] : number

    The position of the item in the collection. The item is pushed to the collection when index not specified.

    Returns

    Collection<T>

    Fires

  • addMany( items, [ index ] ) → Collection<T>

    See source

    Adds multiple items into the collection.

    Any item not containing an id will get an automatically generated one.

    Parameters

    items : Iterable<T>
    [ index ] : number

    The position of the insertion. Items will be appended if no index is specified.

    Returns

    Collection<T>

    Fires

  • bindTo( externalCollection ) → CollectionBindToChain<S, T>

    See source

    Binds and synchronizes the collection with another one.

    The binding can be a simple factory:

    class FactoryClass {
	public label: string;

	constructor( data: { label: string } ) {
		this.label = data.label;
	}
}

const source = new Collection<{ label: string }>( { idProperty: 'label' } );
const target = new Collection<FactoryClass>();

target.bindTo( source ).as( FactoryClass );

source.add( { label: 'foo' } );
source.add( { label: 'bar' } );

console.log( target.length ); // 2
console.log( target.get( 1 ).label ); // 'bar'

source.remove( 0 );
console.log( target.length ); // 1
console.log( target.get( 0 ).label ); // 'bar'

    or the factory driven by a custom callback:

    class FooClass {
	public label: string;

	constructor( data: { label: string } ) {
		this.label = data.label;
	}
}

class BarClass {
	public label: string;

	constructor( data: { label: string } ) {
		this.label = data.label;
	}
}

const source = new Collection<{ label: string }>( { idProperty: 'label' } );
const target = new Collection<FooClass | BarClass>();

target.bindTo( source ).using( ( item ) => {
	if ( item.label == 'foo' ) {
		return new FooClass( item );
	} else {
		return new BarClass( item );
	}
} );

source.add( { label: 'foo' } );
source.add( { label: 'bar' } );

console.log( target.length ); // 2
console.log( target.get( 0 ) instanceof FooClass ); // true
console.log( target.get( 1 ) instanceof BarClass ); // true

    or the factory out of property name:

    const source = new Collection<{ nested: { value: string } }>();
const target = new Collection<{ value: string }>();

target.bindTo( source ).using( 'nested' );

source.add( { nested: { value: 'foo' } } );
source.add( { nested: { value: 'bar' } } );

console.log( target.length ); // 2
console.log( target.get( 0 ).value ); // 'foo'
console.log( target.get( 1 ).value ); // 'bar'

    It's possible to skip specified items by returning null value:

    const source = new Collection<{ hidden: boolean }>();
const target = new Collection<{ hidden: boolean }>();

target.bindTo( source ).using( item => {
	if ( item.hidden ) {
		return null;
	}

	return item;
} );

source.add( { hidden: true } );
source.add( { hidden: false } );

console.log( source.length ); // 2
console.log( target.length ); // 1

    Note: clear can be used to break the binding.

    Type parameters

    S : extends Record<string, any>

    The type of externalCollection element.

    Parameters

    externalCollection : Collection<S>

    A collection to be bound.

    Returns

    CollectionBindToChain<S, T>

    The binding chain object.

  • clear() → void

    See source

    Removes all items from the collection and destroys the binding created using bindTo.

    Returns

    void

    Fires

  • inherited

    delegate( events ) → EmitterMixinDelegateChain

    See source

    Delegates selected events to another Emitter. For instance:

    emitterA.delegate( 'eventX' ).to( emitterB );
emitterA.delegate( 'eventX', 'eventY' ).to( emitterC );

    then eventX is delegated (fired by) emitterB and emitterC along with data:

    emitterA.fire( 'eventX', data );

    and eventY is delegated (fired by) emitterC along with data:

    emitterA.fire( 'eventY', data );

    Parameters

    events : Array<string>

    Event names that will be delegated to another emitter.

    Returns

    EmitterMixinDelegateChain

  • filter( callback, [ ctx ] ) → Array<T>

    See source

    Returns an array with items for which the callback returned a true value.

    Parameters

    callback : ( T, number ) => boolean
    [ ctx ] : any

    Context in which the callback will be called.

    Returns

    Array<T>

    The array with matching items.

  • find( callback, [ ctx ] ) → undefined | T

    See source

    Finds the first item in the collection for which the callback returns a true value.

    Parameters

    callback : ( T, number ) => boolean
    [ ctx ] : any

    Context in which the callback will be called.

    Returns

    undefined | T

    The item for which callback returned a true value.

  • inherited

    fire( eventOrInfo, args ) → GetEventInfo<TEvent>[ 'return' ]

    See source

    Fires an event, executing all callbacks registered for it.

    The first parameter passed to callbacks is an EventInfo object, followed by the optional args provided in the fire() method call.

    Type parameters

    TEvent : extends BaseEvent

    The type describing the event. See BaseEvent.

    Parameters

    eventOrInfo : GetNameOrEventInfo<TEvent>

    The name of the event or EventInfo object if event is delegated.

    args : TEvent[ 'args' ]

    Additional arguments to be passed to the callbacks.

    Returns

    GetEventInfo<TEvent>[ 'return' ]

    By default the method returns undefined. However, the return value can be changed by listeners through modification of the evt.return's property (the event info is the first param of every callback).

  • forEach( callback, [ ctx ] ) → void

    See source

    Performs the specified action for each item in the collection.

    Parameters

    callback : ( T, number ) => unknown
    [ ctx ] : any

    Context in which the callback will be called.

    Returns

    void

  • get( idOrIndex ) → null | T

    See source

    Gets an item by its ID or index.

    Parameters

    idOrIndex : string | number

    The item ID or index in the collection.

    Returns

    null | T

    The requested item or null if such item does not exist.

  • getIndex( itemOrId ) → number

    See source

    Gets an index of an item in the collection. When an item is not defined in the collection, the index will equal -1.

    Parameters

    itemOrId : string | T

    The item or its ID in the collection.

    Returns

    number

    The index of a given item.

  • has( itemOrId ) → boolean

    See source

    Returns a Boolean indicating whether the collection contains an item.

    Parameters

    itemOrId : string | T

    The item or its ID in the collection.

    Returns

    boolean

    true if the collection contains the item, false otherwise.

  • inherited

    listenTo( emitter, event, callback, [ options ] ) → void

    See source

    Registers a callback function to be executed when an event is fired in a specific (emitter) object.

    Events can be grouped in namespaces using :. When namespaced event is fired, it additionally fires all callbacks for that namespace.

    // myEmitter.on( ... ) is a shorthand for myEmitter.listenTo( myEmitter, ... ).
myEmitter.on( 'myGroup', genericCallback );
myEmitter.on( 'myGroup:myEvent', specificCallback );

// genericCallback is fired.
myEmitter.fire( 'myGroup' );
// both genericCallback and specificCallback are fired.
myEmitter.fire( 'myGroup:myEvent' );
// genericCallback is fired even though there are no callbacks for "foo".
myEmitter.fire( 'myGroup:foo' );

    An event callback can stop the event and set the return value of the fire method.

    Type parameters

    TEvent : extends BaseEvent

    The type describing the event. See BaseEvent.

    Parameters

    emitter : Emitter

    The object that fires the event.

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void

  • map( callback, [ ctx ] ) → Array<U>

    See source

    Executes the callback for each item in the collection and composes an array or values returned by this callback.

    Type parameters

    U

    The result type of the callback.

    Parameters

    callback : ( T, number ) => U
    [ ctx ] : any

    Context in which the callback will be called.

    Returns

    Array<U>

    The result of mapping.

  • inherited

    off( event, callback ) → void

    See source

    Stops executing the callback on the given event. Shorthand for this.stopListening( this, event, callback ).

    Parameters

    event : string

    The name of the event.

    callback : Function

    The function to stop being called.

    Returns

    void

  • inherited

    on( event, callback, [ options ] ) → void

    See source

    Registers a callback function to be executed when an event is fired.

    Shorthand for this.listenTo( this, event, callback, options ) (it makes the emitter listen on itself).

    Type parameters

    TEvent : extends BaseEvent

    The type descibing the event. See BaseEvent.

    Parameters

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void

  • inherited

    once( event, callback, [ options ] ) → void

    See source

    Registers a callback function to be executed on the next time the event is fired only. This is similar to calling on followed by off in the callback.

    Type parameters

    TEvent : extends BaseEvent

    The type descibing the event. See BaseEvent.

    Parameters

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void

  • remove( subject ) → T

    See source

    Removes an item from the collection.

    Parameters

    subject : string | number | T

    The item to remove, its ID or index in the collection.

    Returns

    T

    The removed item.

    Fires

  • inherited

    stopDelegating( [ event ], [ emitter ] ) → void

    See source

    Stops delegating events. It can be used at different levels:

    • To stop delegating all events.
    • To stop delegating a specific event to all emitters.
    • To stop delegating a specific event to a specific emitter.

    Parameters

    [ event ] : string

    The name of the event to stop delegating. If omitted, stops it all delegations.

    [ emitter ] : Emitter

    (requires event) The object to stop delegating a particular event to. If omitted, stops delegation of event to all emitters.

    Returns

    void

  • inherited

    stopListening( [ emitter ], [ event ], [ callback ] ) → void

    See source

    Stops listening for events. It can be used at different levels:

    • To stop listening to a specific callback.
    • To stop listening to a specific event.
    • To stop listening to all events fired by a specific object.
    • To stop listening to all events fired by all objects.

    Parameters

    [ emitter ] : Emitter

    The object to stop listening to. If omitted, stops it for all objects.

    [ event ] : string

    (Requires the emitter) The name of the event to stop listening to. If omitted, stops it for all events from emitter.

    [ callback ] : Function

    (Requires the event) The function to be removed from the call list for the given event.

    Returns

    void

  • private

    _getItemIdBeforeAdding( item ) → string

    See source

    Returns an unique id property for a given item.

    The method will generate new id and assign it to the item if it doesn't have any.

    Parameters

    item : any

    Item to be added.

    Returns

    string

  • private

    _remove( subject ) → tuple

    See source

    Core remove method implementation shared in other functions.

    In contrast this method does not fire the event-change event.

    Parameters

    subject : string | number | T

    The item to remove, its id or index in the collection.

    Returns

    tuple

    Returns an array with the removed item and its index.

    Fires

  • private

    _setUpBindToBinding( factory ) → void

    See source

    Finalizes and activates a binding initiated by bindTo.

    Type parameters

    S

    Parameters

    factory : ( S ) => ( null | T )

    A function which produces collection items.

    Returns

    void

Events

  • add( eventInfo, item, index )

    See source

    Fired when an item is added to the collection.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    item : T

    The added item.

    index : number

    An index where the addition occurred.

  • change( eventInfo, data )

    See source

    Fired when the collection was changed due to adding or removing items.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    data : CollectionChangeEventData<T>

    Changed items.

  • remove( eventInfo, item, index )

    See source

    Fired when an item is removed from the collection.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    item : T

    The removed item.

    index : number

    Index from which item was removed.