ReadOnlyObservableCollection

API / ReadOnlyObservableCollection<TItem> class

Represents a read-only observable collection which can be used as a base class for custom observable collections as well.

Extends: ViewModel, implements IReadOnlyObservableCollection<TItem>.

class ReadOnlyObservableCollection<TItem> extends ViewModel implements IReadOnlyObservableCollection<TItem>

Template Parameters

• TItem: the type of items the collection contains.

Constructors

• constructor: initializes a new instance of the ReadOnlyObservableCollection<TItem> class.

Properties

• itemAdded: an event that is raised when an item is added to the collection.
• itemRemoved: an event that is raised when an item is removed from the collection.
• collectionChanged: an event that is raised when the collection changed.
• length: gets the number of items in the collection.
• @unscopables: Returns an object specifying how properties are handled inside a with statement.

Methods

• at: gets the item at the provided index.
• concat: merges the current collection with the given Array(s) and returns a new JavaScript Array.
• join: aggregates the contained items into a String placing the provided separator between them.
• slice: returns a new JavaScript Array containing the elements starting at the provided start index up to, but not including, the provided end index.
• indexOf: returns the first index of an item, or -1 if none can be found.
• lastIndexOf: returns the last index of an item, or -1 if none can be found.
• every: checks whether all elements in the collection fulfil a given condition.
• some: checks whether some elements in the collection fulfil a given condition.
• forEach: executes the given callback for each item in the collection.
• map: creates a new JavaScript Array constructed by mapping each item in the collection using a callback.
• filter: creates a new JavaScript Array containing only the items for which the provided predicate evaluates to true.
• reduce: aggregates the collection to a single value.
• reduceRight: aggregates the collection to a single value by iterating the collection from end to start.
• find: returns the first item for which the provided predicate evaluated to true, if no item can be found then undefined is returned.
• findLast: returns the last item for which the provided predicate evaluated to true, if no item can be found then undefined is returned.
• findIndex: returns the index of the first item for which the provided predicate evaluated to true, if no item can be found then -1 is returned.
• findLastIndex: returns the index of the last item for which the provided predicate evaluated to true, if no item can be found then -1 is returned.
• entries: returns an Array iterator containing all the index/item pairs in the collection.
• keys: returns an Array iterator containing all the indexes in the collection.
• values: returns an Array iterator containing all the items in the collection.
• includes: checks whether the provided item is contained by the collection.
• flatMap: returns a new JavaScript Array by mapping all items in the collection and the flattening the result by one level.
• flat: returns a new JavaScript Array containing the flattened sub-arrays by recursively concatenating them.
• toReversed: Returns a JavaScript Array containing the items of the collection in reverse order.
• toSorted: Returns a JavaScript Array containing the items of the collection in ascending order.
• toSpliced: Returns a JavaScript Array containing the spliced items of the collection.
• with: Returns a JavaScript Array containing the elements from the collection and having the one at the provided index replaced with the provided value.
• @iterator: returns an Array iterator containing all the items in the collection.
• toArray: Converts the observable collection to a native JavaScript Array.

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• push: appends new elements to the end of the collection, and returns the new length of the collection.
• pop: removes the last element from the collection and returns it. If the collection is empty, undefined is returned.
• unshift: inserts new elements at the start of the collection, and returns the new length of the collection.
• shift: removes the first element from the collection and returns it. If the collection is empty, undefined is returned.
• get: gets the item at the provided index.
• set: sets the provided item at the provided index.
• splice: removes and/or adds elements to the collection and returns the deleted elements.
• clear: Clears the contents of the collection and returns the removed items, similar to calling collection.splice(0).
• reset: resets the contents of the collection by clearing it and setting the provided items. Returns the new length of the collection. Similar to calling collection.splice(0, collection.length, ...items).