DLL(doubly linked list) library for javascript projects

Usage no npm install needed!

<script type="module">
  import akashbabuNodeDll from 'https://cdn.skypack.dev/@akashbabu/node-dll';


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DLL(Doubly linked list) implementation for javascript projects


Doubly linked list(DLL) is inevitable in certain situation where performance is preferred while slicing an array (maybe there are more to it, but this is mostly my PoV). So this library was created with a simple, yet powerful interface for interacting with the underlying DLL schema.

This library is written in typescript for robust APIs and type support.

Every aspect was desgined and thought carefully to minimize introducing new bugs.


API method name has been carefully chosen to nearly match Array methods, such that learning curve is least and adaptability is higher. But a few methods couldn't have had a different name and we had to convince ourselves with those method name.


npm i @akashbabu/node-dll -S

Sample usage

import {DLL, DLLItem} from '@akashbabu/node-dll';

const dll = new DLL<string>();

const dllItem: DLLItem<string> = dll.push('foo');
console.log(dllItem.data) // => foo

console.log(dll.length) // => 1

console.log(dll.length) // => 0


const headItem = dll.head
console.log(headItem.data) // => bar

const headData = dll.shift()
console.log(headData) // => bar

console.log(dll.head.data) // => foo

console.log(dll.length) // => 0

const firstItem = dll.push('first')

dll.appendAfter(firstItem, 'second')

dll.forEach((item, i) => {
  console.log(`${i + 1}) ${item}`);
// => 1) first
// => 2) second
// => 3) third

console.log(dll.map((item, i) => `${i + 1}) ${item}`));
// => ["1) first", "2) second", "3) third"]


new DLL():

This creates a new instance of DLL.
T -> Denotes the type of data being saved in DLL

.head: DLLItem | null

Returns the first item in the list

.tail: DLLItem | null

Returns the last item in the list

.length: number

Returns the length of the list

.shift(): T | undefined

Removes and returns the first item in the list. Returns undefined if the list is empty

.unshift(data: T): void

Adds the given item to the head of DLL (same as Array.unshift logic)

.forEach(cb: (data: T, i: number) => void): void

Iterates through the entire DLL

.map(cb: (data: T, i: number) => U): U[]

Iterates through the entire DLL and returns the resultant array.
U -> Denotes the return type of cb(callback)

.push(data: T): DLLItem

Adds the given item to the tail of DLL and returns the added item

.appendAfter(dllItem: DLLItem, data: T): DLLItem

Adds the given data after the given dllItem in DLL and returns the added item

.remove(dllItem: DLLItem): boolean

Removes the given item from DLL and returns true if the removal was successful


Removes all the items in the DLL


DLLItem has a readonly access to prev and next properties, this is to ensure that the users doesn't change them unintentionally (which can mess up with the entire DLL) and hence less surface for bugs.


Set / get data value on the DLLItem via this property


Get prev value on the DLLItem via this property


Get next value on the DLLItem via this property


All contributions are welcome!!!

But before raising any issue, please check the issue-tracker in github if there is any matching issues already in the pipeline, if not then please go ahead and raise your own.

PR Guidelines:

  • Make sure to include corresponding test cases
  • Be generous on code comments
  • Write documentation if necessary
  • Wait for your approval 😜