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)

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

Remove all elements from the collection.

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.

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.

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, opt_silent) inherited

Sets a value.

Name Type Description
key string

Key name.

value *

Value.

silent boolean

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, opt_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

Update without triggering an event.

unset(key, opt_silent) inherited

Unsets a property.

Name Type Description
key string

Key name.

silent boolean

Unset without triggering an event.