Class: Collection

ol/Collection~Collection 


import Collection from 'ol/Collection.js';

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)

Collection.js, line 76
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

changed() inherited

Observable.js, line 68

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

clear()

Collection.js, line 126

Remove all elements from the collection.

dispatchEvent(event){boolean | undefined} inherited

events/Target.js, line 85

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.

extend(arr){Collection<T>}

Collection.js, line 139

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)

Collection.js, line 153

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.

get(key){*} inherited

Object.js, line 135

Gets a value.

Name Type Description
key string

Key name.
Returns:
Value.

getArray(){Array.<T>}

Collection.js, line 168

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

Object.js, line 148

Get a list of object property names.

Returns:
List of property names.

getLength(){number}

Collection.js, line 188

Get the length of this collection.

Returns:
The length of the array.

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

Object.js, line 157

Get an object of all property names and values.

Returns:
Object.

getRevision(){number} inherited

Observable.js, line 79

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

Returns:
Revision.

insertAt(index, elem)

Collection.js, line 198

Insert an element at the provided index.

Name Type Description
index number

Index.
elem T

Element.

item(index){T}

Collection.js, line 178

Get the element at the provided index.

Name Type Description
index number

Index.
Returns:
Element.

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

Observable.js, line 152

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

Observable.js, line 164

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}

Collection.js, line 218

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

Returns:
Element.

push(elem){number}

Collection.js, line 228

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}

Collection.js, line 243

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}

Collection.js, line 260

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

Object.js, line 215

Sets a value.

Name Type Description
key string

Key name.
value *

Value.
silent boolean | undefined

Update without triggering an event.

setAt(index, elem)

Collection.js, line 281

Set the element at the provided index.

Name Type Description
index number

Index.
elem T

Element.

setProperties(values, silent) inherited

Object.js, line 235

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

Observable.js, line 173

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

Object.js, line 259

Unsets a property.

Name Type Description
key string

Key name.
silent boolean | undefined

Unset without triggering an event.