In-memory abstract-leveldown store for Node.js and browsers.

📌 This module will soon be deprecated, because it is superseded by memory-level.

If you are upgrading: please see UPGRADING.md.

const levelup = require('levelup')
const memdown = require('memdown')

const db = levelup(memdown())

db.put('hey', 'you', (err) => {
  if (err) throw err

  db.get('hey', { asBuffer: false }, (err, value) => {
    if (err) throw err
    console.log(value) // 'you'
  })
})

With async/await:

await db.put('hey', 'you')
const value = await db.get('hey', { asBuffer: false })

Your data is discarded when the process ends or you release a reference to the store. Note as well, though the internals of memdown operate synchronously - levelup does not.

Keys and values can be strings or Buffers. Any other key type will be irreversibly stringified. The only exceptions are null and undefined. Keys and values of that type are rejected.

const db = levelup(memdown())

db.put('example', 123, (err) => {
  if (err) throw err

  db.createReadStream({
    keyAsBuffer: false,
    valueAsBuffer: false
  }).on('data', (entry) => {
    console.log(typeof entry.key) // 'string'
    console.log(typeof entry.value) // 'string'
  })
})

If you desire non-destructive encoding (e.g. to store and retrieve numbers as-is), wrap memdown with encoding-down. Alternatively install level-mem which conveniently bundles levelup, memdown and encoding-down. Such an approach is also recommended if you want to achieve universal (isomorphic) behavior. For example, you could have leveldown in a backend and memdown in the frontend.

const encode = require('encoding-down')
const db = levelup(encode(memdown(), { valueEncoding: 'json' }))

db.put('example', 123, (err) => {
  if (err) throw err

  db.createReadStream({
    keyAsBuffer: false,
    valueAsBuffer: false
  }).on('data', (entry) => {
    console.log(typeof entry.key) // 'string'
    console.log(typeof entry.value) // 'number'
  })
})

A memdown store is backed by a fully persistent data structure and thus has snapshot guarantees. Meaning that reads operate on a snapshot in time, unaffected by simultaneous writes.

In addition to the regular npm test, you can test memdown in a browser of choice with:

npm run test-browser-local

To check code coverage:

npm run coverage

Level/memdown is an OPEN Open Source Project. This means that:

Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.

See the Contribution Guide for more details.

Cross-browser Testing Platform and Open Source ♥ Provided by Sauce Labs.

Support us with a monthly donation on Open Collective and help us continue our work.

MIT