level-js is a JavaScript implementation of LevelDB for use in the browser. It provides a simple key-value store API that is compatible with the LevelUP interface, making it easy to use in conjunction with other LevelDB-based libraries.
Basic Key-Value Store
This feature allows you to perform basic key-value operations such as putting, getting, and deleting data in the database.
const level = require('level-js');
const db = level('my-database');
// Put a value
await db.put('key', 'value');
// Get a value
const value = await db.get('key');
console.log(value); // 'value'
// Delete a value
await db.del('key');Batch Operations
Batch operations allow you to perform multiple put and delete operations in a single atomic action, which can be more efficient than performing each operation individually.
const level = require('level-js');
const db = level('my-database');
// Perform batch operations
await db.batch()
.put('key1', 'value1')
.put('key2', 'value2')
.del('key3')
.write();Stream API
The Stream API allows you to create readable and writable streams for iterating over the database entries, which is useful for processing large datasets.
const level = require('level-js');
const db = level('my-database');
// Create a read stream
const stream = db.createReadStream();
stream.on('data', ({ key, value }) => {
console.log(key, value);
});
stream.on('end', () => {
console.log('Stream ended');
});PouchDB is an open-source JavaScript database inspired by Apache CouchDB that is designed to run well within the browser. It provides a similar key-value store functionality but also includes advanced features like synchronization with CouchDB and other PouchDB instances.
LocalForage is a fast and simple storage library for JavaScript. It improves the offline experience of your web app by using asynchronous storage (IndexedDB or WebSQL) with a simple, localStorage-like API. It is more abstracted compared to level-js and is designed to be easier to use.
Dexie.js is a wrapper for IndexedDB that provides a more developer-friendly API. It offers advanced querying capabilities and transaction support, making it a powerful alternative to level-js for complex use cases.
An
abstract-leveldowncompliant store on top of IndexedDB, which is in turn implemented on top of LevelDB which brings this whole shebang full circle.
Here are the goals of level-js:
abstract-leveldown test suiteBuffer keys and valuesnull and undefinedBeing abstract-leveldown compliant means you can use many of the Level modules on top of this library. For some demos of it working, see @brycebaril's presentation Path of the NodeBases Jedi.
If you are upgrading: please see UPGRADING.md.
var levelup = require('levelup')
var leveljs = require('level-js')
var db = levelup(leveljs('bigdata'))
db.put('hello', Buffer.from('world'), function (err) {
if (err) throw err
db.get('hello', function (err, value) {
if (err) throw err
console.log(value.toString()) // 'world'
})
})
In ES6 browsers:
const levelup = require('levelup')
const leveljs = require('level-js')
const db = levelup(leveljs('bigdata'))
await db.put('hello', Buffer.from('world'))
const value = await db.get('hello')
Unlike leveldown, level-js does not stringify keys or values. This means that in addition to strings and Buffers you can store almost any JavaScript type without the need for encoding-down.
All value types of the structured clone algorithm are supported except for null and undefined. Depending on the environment, this includes:
NaN, Infinity and -InfinityIn addition level-js stores Buffer values without transformation. This works in all target environments because Buffer is a subclass of Uint8Array, meaning such values can be passed to IndexedDB as-is.
When getting or iterating binary values, regardless of whether they were stored as a Buffer, ArrayBuffer or a view thereof, values will return as a Buffer. This behavior can be disabled, in which case ArrayBuffer returns as ArrayBuffer, typed arrays return as typed arrays and Buffer returns as Uint8Array:
db.get('key', { asBuffer: false })
db.iterator({ valueAsBuffer: false })
If the environment does not support a type, it will throw an error which level-js catches and passes to the callbacks of put or batch. For example, IE does not support typed array values. At the time of writing, Chrome is the only browser that supports all types listed above.
Due to the special meaning that null and undefined have in abstract-leveldown iterators and Node.js streams, values of this type are converted to empty strings prior to storage.
All key types of IndexedDB Second Edition are supported. Depending on the environment, this includes:
Infinity and -Infinity, but not NaNNaN)In addition you can use Buffer keys, giving level-js the same power as implementations like leveldown and memdown. When iterating binary keys, regardless of whether they were stored as Buffer, ArrayBuffer or a view thereof, keys will return as a Buffer. This behavior can be disabled, in which case binary keys will always return as ArrayBuffer:
db.iterator({ keyAsBuffer: false })
Note that this behavior is slightly different from values due to the way that IndexedDB works. IndexedDB stores binary values using the structured clone algorithm, which preserves views, but it stores binary keys as an array of octets, so that it is able to compare and sort differently typed keys.
If the environment does not support a type, it will throw an error which level-js catches and passes to the callbacks of get, put, del, batch or an iterator. Exceptions are:
null and undefined: rejected early by abstract-leveldownNaN: though invalid per the IndexedDB specification, they are converted to strings for abstract-leveldown compatibility;level-js falls back to String(key).If you desire normalization for keys and values (e.g. to stringify numbers), wrap level-js with encoding-down. Alternatively install level-browserify which conveniently bundles levelup, level-js and encoding-down. Such an approach is also recommended if you want to achieve universal (isomorphic) behavior or to smooth over type differences between browsers. For example, you could have leveldown in a backend and level-js in the frontend.
Another reason you might want to use encoding-down is that the structured clone algorithm, while rich in types, can be slower than JSON.stringify.
For interoperability it is recommended to use Buffer as your binary type. While we recognize that Node.js core modules are moving towards supporting ArrayBuffer and views thereof, Buffer remains the primary binary type in the Level ecosystem.
That said: if you want to put() an ArrayBuffer you can! Just know that it will come back as a Buffer by default. If you want to get() or iterate stored ArrayBuffer data as an ArrayBuffer, you have a few options. Without encoding-down:
const db = levelup(leveljs('mydb'))
// Yields an ArrayBuffer, Buffer and ArrayBuffer
const value1 = await db.get('key', { asBuffer: false })
const value2 = await db.get('key')
const value3 = value2.buffer
With encoding-down (or level-browserify) you can use the id encoding to selectively bypass encodings:
const encode = require('encoding-down')
const db = levelup(encode(leveljs('mydb'), { valueEncoding: 'binary' }))
// Yields an ArrayBuffer, Buffer and ArrayBuffer
const value1 = await db.get('key', { valueEncoding: 'id' })
const value2 = await db.get('key')
const value3 = value2.buffer
With npm do:
npm install level-js
Not to be confused with leveljs.
This library is best used with browserify.
db = leveljs(location[, options])Returns a new leveljs instance. location is the string name of the IDBDatabase to be opened, as well as the object store within that database. The database name will be prefixed with options.prefix.
optionsThe optional options argument may contain:
prefix (string, default: 'level-js-'): Prefix for IDBDatabase name.version (string | number, default: 1): The version to open the database with.See IDBFactory#open for more details.
git clone git@github.com:Level/level-js.git
cd level-js
npm install
npm test
It will print out a URL to open in a browser of choice.
Cross-browser Testing Platform and Open Source ♥ Provided by Sauce Labs.
MIT © 2012-present Max Ogden and Contributors.
FAQs
An abstract-leveldown compliant store on top of IndexedDB
We found that level-js demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 3 open source maintainers collaborating on the project.
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