@akashbabu/node-dll

node-dll

DLL(Doubly linked list) implementation for javascript projects

Introduction

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.

Documentation

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.

Installation

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

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

dll.push('foo')
dll.unshift('bar')

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

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

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

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

const firstItem = dll.push('first')
dll.push('third')

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"]

API - DLL

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

.clear()

Removes all the items in the DLL

API - DLLItem

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.

.data

Set / get data value on the DLLItem via this property

.prev

Get prev value on the DLLItem via this property

.next

Get next value on the DLLItem via this property

Contribution

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 😜

Licence

MIT