Idb-request NPM

idb-request

Transform IndexedDB request-like object to a Promise.

Promise is a nice way to deal with primitives of IndexedDB. IDBRequest has onsuccess and onerror callbacks, which perfectly map to Promise's resolve and reject. The same applies to oncomplete and onerror of IDBTransaction.

If you're going to reuse transactions with Promise syntax, you can't be sure that it will work in all browsers. You need to rely on the default callback syntax or use idb-batch. This issue is well explained in "Tasks, microtasks, queues and schedules" article.

Internally idb-request fixes IndexedDBShim#204 issue and allows safely iterate over index cursors.

Installation

npm install --save idb-request

Example

Using ES2016 async/await syntax.

import { open } from 'idb-factory'
import { request, requestTransaction, requestCursor } from 'idb-request'
import map from 'lodash.map'

async () => {  
  const db = await open('mydb', 1, upgradeCallback)
  const tr = db.transaction(['books'], 'readwrite')
  const books = tr.objectStore('books')

  await Promise.all([
    request(books.put({ id: 1, title: 'Quarry Memories', author: 'Fred' })),
    request(books.put({ id: 2, title: 'Water Buffaloes', author: 'Fred' })),
    request(books.put({ id: 3, title: 'Bedrock Nights', author: 'Barney' })),
    requestTransaction(tr),
  ])

  const req = books.index('byAuthor').openCursor(null, 'nextunique') // works everywhere
  const result = []
  await requestCursor(req, (cursor) => {
    result.push(cursor.value)
    cursor.continue()
  })

  console.assert(map(result, 'author') === ['Barney', 'Fred'])
}()

function upgradeCallback(e) {
  const books = e.target.result.createObjectStore('books', { keyPath: 'id' })
  books.createIndex('byTitle', 'title', { unique: true })
  books.createIndex('byAuthor', 'author')
}

API

Each function returns a Promise.

request(req, tr)

Listen to request's onsuccess event.

import { request } from 'idb-request'

const books = db.transaction(['books'], 'readonly').objectStore('books')
request(books.count()).then((count) => {})

Pass the transaction as a second argument to await completion and return the result of the request.

import { request } from 'idb-request'

const tr = db.transaction(['books'], 'readwrite')
const books = tr.objectStore('books')
const req = books.put({ title: 'Store 1' })

request(req, tr).then((requestResult) => {})

mapCursor(req, iterator)

Map values over cursor. Iterator has 3 arguments:

cursor object,
result array, which is returned on resolve. Default value is [].
stop resolve promise and exit earlier

import { mapCursor } from 'idb-request'

const limit = 10
const result = await mapCursor(books.openCursor(), (cursor, memo, stop) => {
  memo.push(cursor.value)
  if (memo.length >= limit) stop()
  else cursor.continue()
})

requestCursor(req, iterator)

Iterate through object store or index using cursor.

The same example as mapCursor above:

import { requestCursor } from 'idb-request'

const limit = 10
const result = []
const req = books.openCursor()

await requestCursor(req, (cursor, stop) => {
  result.push(cursor.value)
  if (memo.length >= limit) stop()
  else cursor.continue()
})

// use result array

requestTransaction(tr)

Listen to transaction's oncomplete event.

import { request, requestTransaction } from 'idb-request'

const tr = db.transaction(['books'], 'readwrite')
const books = tr.objectStore('books')

await Promise.all([
  request(books.put({ id: 1, title: 'Quarry Memories' })),
  request(books.put({ id: 2, title: 'Water Buffaloes' })),
  request(books.put({ id: 3, title: 'Bedrock Nights' })),
  requestTransaction(tr),
])