fixed-size-list

Immutable fixed-length list (a.k.a circular buffer) with an event emitter for Typescript and Javascript

• Quick start
• Initial list
• Events
  • eventNewItem
  • eventTruncate
  • eventReset
  • eventCreated
• API

Quick start

npm i fixed-size-list

import { FixedSizeList } from 'fixed-size-list'

const maxSize = 3
const fixedSizeList = new FixedSizeList<number>(maxSize)
// Now it's empty
fixedSizeList.add(1)
// Not it's [ 1 ]
fixedSizeList.add(2)
// Now it's [ 2, 1 ]
fixedSizeList.add(3)
// Now it's [ 3, 2, 1 ]
fixedSizeList.add(4)
// Now it's [ 4, 3, 2 ]

console.log(fixedSizeList.data)
// logs [4,3,2]

fixedSizeList.reset()
// Now it's []

Initial list

You can set initial values easily passing them to the constructor

import { FixedSizeList } from 'fixed-size-list'

const maxSize = 3
const list = [1, 2, 3]
const fixedSizeList = new FixedSizeList<number>(maxSize, list)
// Now it's [ 1, 2, 3 ]

Be aware that the initial list is truncated if it's longer than maxSize

import { FixedSizeList } from 'fixed-size-list'

const maxSize = 2
const list = [1, 2, 3]
const fixedSizeList = new FixedSizeList<number>(maxSize, list)
// Now it's [ 1, 2 ]
// 3 was truncated

Events

FixedSizeList has an event emitter. You can listen to specific events. WARNING! on returns an unsubscribe function. Do not forget to call it when you no longer need the subscription to unsubscribe.

eventNewItem

It emits an added item

import { FixedSizeList, eventNewItem } from 'fixed-size-list'

const maxSize = 2
const fixedSizeList = new FixedSizeList<number>(maxSize)
const unsubscribe = fixedSizeList.on(eventNewItem, (newItem) => console.log('item added', newItem))
fixedSizeList.add(5)
// logs 'item added 5'

// later on
unsubscribe()

eventTruncate

It emits an array of removed items

import { FixedSizeList, eventTruncate } from 'fixed-size-list'

const maxSize = 2
const fixedSizeList = new FixedSizeList<number>(maxSize)
const unsubscribe = fixedSizeList.on(eventTruncate, (removedItems) =>
  console.log('items removed', removedItems.toString()),
)
fixedSizeList.add(5)
fixedSizeList.add(4)
fixedSizeList.add(3)
// logs 'items removed [ 5 ]'

// later on
unsubscribe()

eventReset

import { FixedSizeList, eventReset } from 'fixed-size-list'

const maxSize = 2
const fixedSizeList = new FixedSizeList<number>(maxSize)
const unsubscribe = fixedSizeList.on(eventReset, () => console.log('list reset'))
fixedSizeList.reset()
// logs 'list reset'

// later on
unsubscribe()

eventCreated

We can add the third optional parameter of FixedSizeList's constructor and pass a custom event emitter

import { FixedSizeList, eventCreated, IFixedSizeListEvents } from 'fixed-size-list'
import mitt from 'mitt'

const maxSize = 2
const list = []
const emitter = mitt()
const unsubscribe = emitter.on(eventCreated, () => console.log('list created'))

const fixedSizeList = new FixedSizeList<number>(maxSize, list, emitter)
// logs 'list created'

// later on
unsubscribe()

All

We can subscribe to all events at once

import { FixedSizeList, eventCreated, IFixedSizeListEvents } from 'fixed-size-list'

const fixedSizeList = new FixedSizeList<number>(10)
const unsubscribe = emitter.on('*', () => console.log('Any event'))

// later on
unsubscribe()