Package Exports

@adiwajshing/keyed-db

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Readme

Keyed DB

A light-weight node library to manage a sorted & indexed collection with pagination support. All done using Binary Search. Based off my swift code for Queenfisher

Install

npm i github:adiwajshing/keyed-db

Running Tests

npm test

Functions

db = new KeyedDB<T> (t => t.uniqueNumberKeyProperty, t => t.optionalUniqueIDProperty)
db.insert (value) // insert value in DB
db.delete (value) // delete value
db.updateKey (value, value => value.uniqueKeyProperty = newValue) // update the key of a value
db.paginated (someCursor, 20) // get X results after the given cursor (null for the first X results)

Usage

import KeyedDB from '@adiwajshing/keyed-db'

// Let's use the db to sort & maintain a list of chats
// Chats must be accessed quickly via the chatID (the person you're chatting with)
// Chats must be sorted by recency
type Chat = {
    timestamp: Date
    chatID: string
}

// first argument -- sorting property, second argument -- ID property
const db = new KeyedDB<Chat>(value => value.timestamp.getTime()*-1, value => value.chatID)

for (let i = 0; i < 1000;i++) {
    // insert data
    db.insert (
        {
            timestamp: new Date( new Date().getTime() - Math.random()*10000 ), 
            chatID: `person ${i}`
        }
    )
}
console.log (db.all()) // return sorted array
console.log (db.paginated(null, 20)) // return first 20 chats

const someDate = new Date().getTime()
const cursorPaginated = db.paginated(someDate, 20)
console.log (cursorPaginated) // return 20 chats after the specified date

db.delete (cursorPaginated[0]) // delete paginated chats 

// update chat timestamp
db.updateKey(cursorPaginated[1], value => value.timestamp = new Date().getTime())

Time Complexity

Operation	Time Complexity
db.insert()	O(logN)
db.delete()	O(logN)
db.get()	O(1)
db.updateKey()	O(logN)