Round Linked Queue

Implements a fixed-size linked-list based queue. When trying to add an element to a full queue, it will evict the first added item in order to make room for the new element. This queue preserves the First In/First Out operation mode.

How it works?

Given a queue of capacity 3, initially empty:

(Nil)

Calling queue.add(1) will put 1 at the beginning of the queue:

(1) -> (Nil)

Then queue.add(2) will turn it into:

(1) -> (2) -> (Nil)

Once more, with queue.add(3) we will have:

(1) -> (2) -> (3) -> (Nil)

Now the queue is at capacity. If we try to add another element, it will remove the element that was added first and shift all elements to the right. Consider queue.add(4), the final result will be:

(2) -> (3) -> (4) -> (Nil)

(1) // <--- removed element will be returned

Installation

yarn add round-linked-queue
# or with NPM
# npm install --save round-linked-queue

API

constructor

new RoundLinkedQueue(maxLength: number) => RoudLinkedQueue

Params:

• maxLength: number: the capacity of the queue.

#add()

add(element: Any) => Any

Params:

• element: Any: the element to add to the queue.

Returns:

• undefined: if the queue is not at capacity, because no element was removed.
• Any: the removed element if the queue is at capacity.

#remove()

remove() => Any, throws Error

Returns:

• Any: the removed element if the queue is not empty.

Throws:

• Error: if the queue is empty.

#toArray()

toArray() => [Any]

Returns:

• [Any]: an Array with all elements in the queue.

#*[Symbol.iterator]()

*[Symbol.iterator]() => [Any]

Returns:

• Iterator: an iterator for the queue.

.maxLength

get maxLength => Number

Returns:

• Number: the capacity of the queue.

.first

get first => Any, throws Error

Returns:

• Any: the first element in the queue if it is not empty.

Throws:

• Error: if the queue is empty.

.last

get last => Any, throws Error

Returns:

• Any: the last element in the queue if it is not empty.

Throws:

• Error: if the queue is empty.

static fromArray

RoundLinkedQueue.fromArray(inputArray: [Any]) => RoudLinkedQueue

Params:

• inputArray: [Any]: an arbitrary array of elements.

Returns:

• RoundLinkedQueue: a new instance of the queue containing all elements in the array, respecting the insertion order.

Contributing

Running tests

After clonnig this repo, run:

yarn test **.test.js
# or with NPM
# npm run test **.test.js