dubc-ds-ar

An observable array, backed by a native JavaScript array.

Note that this class follows the conventions of other dubc-ds observable data structures, so the semantics are subtly different than what you're used to with native JavaScript arrays. In general, this version is much stricter:

1. Bounds are always checked, and invalid indices always throw an error.

Constructor

constructor()

Creates an empty deque. To pre-populate a deque, you can use the static of method:

import { Deque } from "dubc-ds-deque"

const d = Deque.of("1", "2", "3")

Properties

.first O(1)

Returns the first value in the deque, or undefined if the deque is empty.

.i O(1)

Returns an iterator over the values in the deque.

.last O(1)

Returns the last value in the deque, or undefined if the deque is empty.

.only O(1)

Returns the only value in the deque. If the deque doesn't have exactly one element, throws an Error.

.size O(1)

Returns the number of values in the deque.

Methods

.clear() O(1)

Removes all values from the deque.

.drop(f:(x:T)=>boolean) O(n)

Removes every element from the deque that matches the given predicate, and returns the number of items that were dropped.

.hear(keeper:object, f:(event:DSEvent<T>)) O(1)

Adds a listener to the deque. Any time the deque changes (and only when the deque actually changes), the listener function will be called.

The listener function is also called immediately with the current contents of the deque.

The keeper parameter keeps a strong reference to the function. You will generally want to pass the web component that's listening for changes to the deque.

Returns a number that can be sent to unhear to stop receiving events.

.pop() O(1)

Removes the last value from the deque and returns it. Returns undefined if the deque is empty.

.push(value:T) O(1)

Adds a value to the end of the deque.

.replace(i:Iterable<T>) O(k)

Replaces the content of this deque with new values.

.reversed() O(1)

Returns an iterable iterator over the values in the deque, in reverse sort order.

.shift() O(1)

Removes the first value from the deque and returns it. Returns undefined if the deque is empty.

.unhear(n:number) O(1)

Removes the listener registered with the specified number.

.unshift(v:T) O(1)

Adds a value to the beginning of the deque.

Operations by Kind

Listeners

• hear(eventHandler) get events when the deque changes
• unhear(n) stop listening for changes

Iterators

• Deque itself is an iterable, so you can use it directly in for...of
• i to get an iterator
• reversed() to iterate backwards

Values

• first get the first value
• last get the last value
• only get the only value
• size get the number of values

Changing

• pop() remove the last value
• push() add a value to the end
• shift() remove the first value
• unshift() add a value to the beginning

Bulk

• clear() remove all values
• replace(values) clear the deque then add many values
• drop(predicate) removes all values that match the predicate