Class: Collection

ol/Collection~Collection


import Collection from 'ol/Collection';

An expanded version of standard JS Array, adding convenience methods for manipulation. Add and remove changes to the Collection trigger a Collection event. Note that this does not cover changes to the objects within the Collection; they trigger events on the appropriate object, not on the Collection as a whole.

new Collection(array, options)

Name Type Description
array Array.<T> | undefined

Array.

options

Collection options.

Name Type Description
unique boolean (defaults to false)

Disallow the same item from being added to the collection twice.

Fires:

Extends

Observable Properties

Name Type Settable ObjectEvent type Description
length number no change:length

The length of the array.

Methods

Increases the revision counter and dispatches a 'change' event.

Remove all elements from the collection.

dispatchEvent(event){boolean | undefined} inherited

Dispatches an event and calls all listeners listening for events of this type. The event parameter can either be a string or an Object with a type property.

Name Type Description
event BaseEvent | string

Event object.

Returns:
false if anyone called preventDefault on the event object or if any of the listeners returned false.

Add elements to the collection. This pushes each item in the provided array to the end of the collection.

Name Type Description
arr Array.<T>

Array.

Returns:
This collection.

forEach(f)

Iterate over each element, calling the provided callback.

Name Type Description
f function

The function to call for every element. This function takes 3 arguments (the element, the index and the array). The return value is ignored.

Gets a value.

Name Type Description
key string

Key name.

Returns:
Value.

getArray(){Array.<T>}

Get a reference to the underlying Array object. Warning: if the array is mutated, no events will be dispatched by the collection, and the collection's "length" property won't be in sync with the actual length of the array.

Returns:
Array.

getKeys(){Array.<string>} inherited

Get a list of object property names.

Returns:
List of property names.

getLength(){number}

Get the length of this collection.

Returns:
The length of the array.

getProperties(){Object.<string, *>} inherited

Get an object of all property names and values.

Returns:
Object.

getRevision(){number} inherited

Get the version number for this object. Each time the object is modified, its version number will be incremented.

Returns:
Revision.

insertAt(index, elem)

Insert an element at the provided index.

Name Type Description
index number

Index.

elem T

Element.

item(index){T}

Get the element at the provided index.

Name Type Description
index number

Index.

Returns:
Element.

on(type, listener){EventsKey | Array<EventsKey>} inherited

Listen for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.

listener function

The listener function.

Returns:
Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

once(type, listener){EventsKey | Array<EventsKey>} inherited

Listen once for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.

listener function

The listener function.

Returns:
Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

pop(){T | undefined}

Remove the last element of the collection and return it. Return undefined if the collection is empty.

Returns:
Element.

push(elem){number}

Insert the provided element at the end of the collection.

Name Type Description
elem T

Element.

Returns:
New length of the collection.

remove(elem){T | undefined}

Remove the first occurrence of an element from the collection.

Name Type Description
elem T

Element.

Returns:
The removed element or undefined if none found.

removeAt(index){T | undefined}

Remove the element at the provided index and return it. Return undefined if the collection does not contain this index.

Name Type Description
index number

Index.

Returns:
Value.

set(key, value, silent) inherited

Sets a value.

Name Type Description
key string

Key name.

value *

Value.

silent boolean | undefined

Update without triggering an event.

setAt(index, elem)

Set the element at the provided index.

Name Type Description
index number

Index.

elem T

Element.

setProperties(values, silent) inherited

Sets a collection of key-value pairs. Note that this changes any existing properties and adds new ones (it does not remove any existing properties).

Name Type Description
values Object.<string, *>

Values.

silent boolean | undefined

Update without triggering an event.

un(type, listener) inherited

Unlisten for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.

listener function

The listener function.

unset(key, silent) inherited

Unsets a property.

Name Type Description
key string

Key name.

silent boolean | undefined

Unset without triggering an event.