memdown
Version:
An drop-in replacement for LevelDOWN that works in memory only
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Markdown
> In-memory [`abstract-leveldown`] store for Node.js and browsers.
[![level badge][level-badge]](https://github.com/Level/awesome)
[](https://www.npmjs.com/package/memdown)
[](https://www.npmjs.com/package/memdown)
[](https://github.com/Level/memdown/actions/workflows/test.yml)
[](https://codecov.io/gh/Level/memdown)
[](https://standardjs.com)
[](https://common-changelog.org)
[](https://opencollective.com/level)
_If you are upgrading: please see [`UPGRADING.md`](./UPGRADING.md)._
```js
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`:
```js
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.
[](https://app.saucelabs.com/u/level-ci)
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.
```js
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.
```js
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](https://www.npmjs.com/package/functional-red-black-tree) 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`](https://github.com/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](https://github.com/Level/community/blob/master/CONTRIBUTING.md) for more details.
Cross-browser Testing Platform and Open Source ♥ Provided by [Sauce Labs](https://saucelabs.com).
[](https://saucelabs.com)
Support us with a monthly donation on [Open Collective](https://opencollective.com/level) and help us continue our work.
[](LICENSE)
[`abstract-leveldown`]: https://github.com/Level/abstract-leveldown
[`levelup`]: https://github.com/Level/levelup
[`encoding-down`]: https://github.com/Level/encoding-down
[`leveldown`]: https://github.com/Level/leveldown
[`level-mem`]: https://github.com/Level/mem
[]: https://leveljs.org/img/badge.svg