linked-list
Small double linked list.
Contents
- What is this?
- When should I use this?
- Install
- Use
- API
- Types
- Compatibility
- Security
- Contribute
- License
What is this?
This package is a small double linked list. Items in linked lists know about their next sibling (the item after them). In double linked lists, items also know about their previous sibling (the item before them).
When should I use this?
You can use this project as a reference for how to implement a linked list but it’s also definitely possible to use it, directly or by subclassing its lists and items.
Install
This package is ESM only. In Node.js (version 14.14+, 16.0+), install with npm:
npm install linked-listIn Deno with esm.sh:
import {List, Item} from 'https://esm.sh/linked-list@3'In browsers with esm.sh:
<script type="module">
import {List, Item} from 'https://esm.sh/linked-list@3?bundle'
</script>Use
import {List, Item} from 'linked-list'
const item1 = new Item()
const item2 = new Item()
const item3 = new Item()
const list = new List(item1, item2, item3)
list.head // => item1
list.head.next // => item2
list.head.next.next // => item3
list.head.next.prev // => item1
list.tail // => item3
list.tail.next // => `null`Subclassing:
import {List, Item} from 'linked-list'
class Tokens extends List {
/** @param {string} delimiter */
join(delimiter) {
return this.toArray().join(delimiter)
}
}
class Token extends Item {
/** @param {string} value */
constructor(value) {
super()
this.value = value
}
toString() {
return this.value
}
}
const dogs = new Token('dogs')
const and = new Token('&')
const cats = new Token('cats')
const tokens = new Tokens(dogs, and, cats)
console.log(tokens.join(' ')) // => 'dogs & cats'
and.prepend(cats)
and.append(dogs)
console.log(tokens.join(' ') + '!') // => 'cats & dogs!'API
This package exports the identifiers List and Item.
There is no default export.
List([items…])
new List()
new List(new Item(), new Item())Create a new list from the given items.
Ignores null or undefined values.
Throws an error when a given item has no detach, append, or prepend
methods.
List.from([items])
List.from()
List.from([])
List.from([new Item(), new Item()])Create a new this from the given array of items.
Ignores null or undefined values.
Throws an error when a given item has no detach, append, or prepend
methods.
List.of([items…])
List.of()
List.of(new Item(), new Item())Create a new this from the given arguments.
Ignores null or undefined values.
Throws an error when a given item has no detach, append, or prepend
methods.
List#append(item)
const list = new List()
const item = new Item()
console.log(list.head === null) // => true
console.log(item.list === null) // => true
list.append(item)
console.log(list.head === item) // => true
console.log(item.list === list) // => trueAppend an item to a list.
Throws an error when the given item has no detach, append, or prepend
methods.
Returns the given item.
List#prepend(item)
const list = new List()
const item = new Item()
list.prepend(item)Prepend an item to a list.
Throws an error when the given item has no detach, append, or prepend
methods.
Returns the given item.
List#toArray()
const item1 = new Item()
const item2 = new Item()
const list = new List(item1, item2)
const array = list.toArray()
console.log(array[0] === item1) // => true
console.log(array[1] === item2) // => true
console.log(array[0].next === item2) // => true
console.log(array[1].prev === item1) // => trueReturns the items of the list as an array.
This does not detach the items.
Note:
Listalso implements an iterator. That means you can also do[...list]to get an array.
List#head
const item = new Item()
const list = new List(item)
console.log(list.head === item) // => trueThe first item in a list or null otherwise.
List#tail
const list = new List()
const item1 = new Item()
const item2 = new Item()
console.log(list.tail === null) // => true
list.append(item1)
console.log(list.tail === null) // => true, see note.
list.append(item2)
console.log(list.tail === item2) // => trueThe last item in a list and null otherwise.
👉 Note: a list with only one item has no tail, only a head.
List#size
const list = new List()
const item1 = new Item()
const item2 = new Item()
console.log(list.size === 0) // => true
list.append(item1)
console.log(list.size === 1) // => true
list.append(item2)
console.log(list.size === 2) // => trueThe number of items in the list.
Item()
const item = new Item()Create a new linked list item.
Item#append(item)
const item1 = new Item()
const item2 = new Item()
new List().append(item1)
console.log(item1.next === null) // => true
item1.append(item2)
console.log(item1.next === item2) // => trueAdd the given item after the operated on item in a list.
Throws an error when the given item has no detach, append, or prepend
methods.
Returns false when the operated on item is not attached to a list, otherwise
the given item.
Item#prepend(item)
const item1 = new Item()
const item2 = new Item()
new List().append(item1)
console.log(item1.prev === null) // => true
item1.prepend(item2)
console.log(item1.prev === item2) // => trueAdd the given item before the operated on item in a list.
Throws an error when the given item has no detach, append, or prepend
methods.
Returns false when the operated on item is not attached to a list, otherwise
the given item.
Item#detach()
const item = new Item()
const list = new List(item)
console.log(item.list === list) // => true
item.detach()
console.log(item.list === null) // => trueRemove the operated on item from its parent list.
Removes references to it on its parent list, and prev and next items.
Relinks all references.
Returns the operated on item.
Even when it was already detached.
Item#next
const item1 = new Item()
const item2 = new Item()
const list = new List(item1)
console.log(item1.next === null) // => true
console.log(item2.next === null) // => true
item1.append(item2)
console.log(item1.next === item2) // => true
item1.detach()
console.log(item1.next === null) // => trueThe following item or null otherwise.
Item#prev
const item1 = new Item()
const item2 = new Item()
const list = new List(item1)
console.log(item1.prev === null) // => true
console.log(item2.prev === null) // => true
item1.append(item2)
console.log(item2.prev === item1) // => true
item2.detach()
console.log(item2.prev === null) // => trueThe preceding item or null otherwise.
Item#list
const item = new Item()
const list = new List()
console.log(item.list === null) // => true
list.append(item)
console.log(item.list === list) // => true
item.detach()
console.log(item.list === null) // => trueThe list this item belongs to or null otherwise.
Types
This package is fully typed with TypeScript. It exports no additional types.
Compatibility
This package is at least compatible with all maintained versions of Node.js. As of now, that is Node.js 14.14+ and 16.0+. It also works in Deno and modern browsers.
Security
This package is safe.
Contribute
Yes please! See How to Contribute to Open Source.