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(opt_array, opt_options)

Collection.js, line 68
Name Type Description
array Array.<T>

Array.

options

Collection options.

Name Type Default Description
unique boolean false

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

Fires:

Extends

Observable Properties

Name Type Settable ol/Object~ObjectEvent type Description
length number no change:length

The length of the array.

Methods

changed() inherited

Observable.js, line 59

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

clear()

Collection.js, line 103

Remove all elements from the collection.

dispatchEvent(event) inherited

Observable.js, line 76

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 Object | module:ol/events/Event~Event | string

Event object.

extend(arr){module:ol/Collection~Collection.<T>}

Collection.js, line 117

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 132

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 136

Gets a value.

Name Type Description
key string

Key name.

Returns:
Value.

getArray(){Array.<T>}

Collection.js, line 148

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 150

Get a list of object property names.

Returns:
List of property names.

getLength(){number}

Collection.js, line 170

Get the length of this collection.

Returns:
The length of the array.

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

Object.js, line 160

Get an object of all property names and values.

Returns:
Object.

getRevision(){number} inherited

Observable.js, line 85

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 181

Insert an element at the provided index.

Name Type Description
index number

Index.

elem T

Element.

item(index){T}

Collection.js, line 159

Get the element at the provided index.

Name Type Description
index number

Index.

Returns:
Element.

on(type, listener){module:ol/events~EventsKey|Array.<module:ol/events~EventsKey>} inherited

Observable.js, line 99

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){module:ol/events~EventsKey|Array.<module:ol/events~EventsKey>} inherited

Observable.js, line 122

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 198

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 209

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 225

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 243

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, opt_silent) inherited

Object.js, line 185

Sets a value.

Name Type Description
key string

Key name.

value *

Value.

silent boolean

Update without triggering an event.

setAt(index, elem)

Collection.js, line 258

Set the element at the provided index.

Name Type Description
index number

Index.

elem T

Element.

setProperties(values, opt_silent) inherited

Object.js, line 205

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

Update without triggering an event.

un(type, listener) inherited

Observable.js, line 142

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, opt_silent) inherited

Object.js, line 218

Unsets a property.

Name Type Description
key string

Key name.

silent boolean

Unset without triggering an event.