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179 lines
6.7 KiB
179 lines
6.7 KiB
4 years ago
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# level-js
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> An [`abstract-leveldown`][abstract-leveldown] compliant store on top of [IndexedDB][indexeddb].
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[![level badge][level-badge]][awesome]
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[](https://www.npmjs.com/package/level-js)
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[](https://travis-ci.com/Level/level-js)
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[](https://www.npmjs.com/package/level-js)
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[](https://coveralls.io/github/Level/level-js)
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[](https://standardjs.com)
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[](#backers)
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[](#sponsors)
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## Table of Contents
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<details><summary>Click to expand</summary>
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- [Background](#background)
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- [Example](#example)
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- [Browser Support](#browser-support)
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- [Type Support](#type-support)
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- [Install](#install)
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- [API](#api)
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- [Running Tests](#running-tests)
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- [Big Thanks](#big-thanks)
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- [Contributing](#contributing)
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- [Donate](#donate)
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- [License](#license)
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</details>
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## Background
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Here are the goals of `level-js`:
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- Store large amounts of data in modern browsers
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- Pass the full [`abstract-leveldown`][abstract-leveldown] test suite
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- Support string and [`Buffer`][buffer] keys and values
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- Be as fast as possible
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- ~~Sync with [multilevel](https://github.com/juliangruber/multilevel) over ASCII or binary transports.~~
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Being `abstract-leveldown` compliant means you can use many of the [Level modules][awesome] on top of this library.
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## Example
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**If you are upgrading:** please see [UPGRADING.md](UPGRADING.md).
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```js
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var levelup = require('levelup')
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var leveljs = require('level-js')
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var db = levelup(leveljs('bigdata'))
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db.put('hello', Buffer.from('world'), function (err) {
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if (err) throw err
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db.get('hello', function (err, value) {
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if (err) throw err
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console.log(value.toString()) // 'world'
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})
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})
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```
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In ES6 browsers:
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```js
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const levelup = require('levelup')
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const leveljs = require('level-js')
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const db = levelup(leveljs('bigdata'))
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await db.put('hello', Buffer.from('world'))
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const value = await db.get('hello')
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```
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## Browser Support
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[](https://saucelabs.com/u/level-js)
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## Type Support
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Keys and values can be a string or [`Buffer`][buffer]. Any other type will be irreversibly stringified. The only exceptions are `null` and `undefined`. Keys and values of that type are rejected.
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In order to sort string and Buffer keys the same way, for compatibility with `leveldown` and the larger ecosystem, `level-js` internally converts keys and values to binary before passing them to IndexedDB. If binary keys are not supported by the environment (like IE11) `level-js` falls back to `String(key)`.
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If you desire non-destructive encoding (e.g. to store and retrieve numbers as-is), wrap `level-js` with [`encoding-down`][encoding-down]. Alternatively install [`level`][level] which conveniently bundles [`levelup`][levelup], `level-js` and `encoding-down`. Such an approach is also recommended if you want to achieve universal (isomorphic) behavior. For example, you could have [`leveldown`][leveldown] in a backend and `level-js` in the frontend. The `level` package does exactly that.
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When getting or iterating keys and values, regardless of the type with which they were stored, keys and values will return as a Buffer unless the `asBuffer`, `keyAsBuffer` or `valueAsBuffer` options are set, in which case strings are returned. Setting these options is not needed when `level-js` is wrapped with `encoding-down`, which determines the optimal return type by the chosen encoding.
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```js
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db.get('key', { asBuffer: false })
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db.iterator({ keyAsBuffer: false, valueAsBuffer: false })
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```
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## Install
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With [npm](https://npmjs.org) do:
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```bash
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npm install level-js
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```
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Not to be confused with [leveljs](https://www.npmjs.com/package/leveljs).
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This library is best used with [browserify](http://browserify.org).
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## API
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### `db = leveljs(location[, options])`
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Returns a new `leveljs` instance. `location` is the string name of the [`IDBDatabase`](https://developer.mozilla.org/en-US/docs/Web/API/IDBDatabase) to be opened, as well as the object store within that database. The database name will be prefixed with `options.prefix`.
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#### `options`
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The optional `options` argument may contain:
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- `prefix` _(string, default: `'level-js-'`)_: Prefix for `IDBDatabase` name.
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- `version` _(string | number, default: `1`)_: The version to open the database with.
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See [`IDBFactory#open`](https://developer.mozilla.org/en-US/docs/Web/API/IDBFactory/open) for more details.
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## Running Tests
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```sh
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git clone git@github.com:Level/level-js.git
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cd level-js
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npm install
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npm test
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```
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It will print out a URL to open in a browser of choice.
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## Big Thanks
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Cross-browser Testing Platform and Open Source ♥ Provided by [Sauce Labs](https://saucelabs.com).
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[](https://saucelabs.com)
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## Contributing
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[`Level/level-js`](https://github.com/Level/level-js) is an **OPEN Open Source Project**. This means that:
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> 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.
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See the [Contribution Guide](https://github.com/Level/community/blob/master/CONTRIBUTING.md) for more details.
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## Donate
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To sustain [`Level`](https://github.com/Level) and its activities, become a backer or sponsor on [Open Collective](https://opencollective.com/level). Your logo or avatar will be displayed on our 28+ [GitHub repositories](https://github.com/Level) and [npm](https://www.npmjs.com/) packages. 💖
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### Backers
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[](https://opencollective.com/level)
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### Sponsors
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[](https://opencollective.com/level)
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## License
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[MIT](LICENSE.md) © 2012-present [Max Ogden](https://github.com/maxogden) and [Contributors](CONTRIBUTORS.md).
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[level-badge]: https://leveljs.org/img/badge.svg
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[indexeddb]: https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API
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[buffer]: https://nodejs.org/api/buffer.html
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[awesome]: https://github.com/Level/awesome
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[abstract-leveldown]: https://github.com/Level/abstract-leveldown
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[levelup]: https://github.com/Level/levelup
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[leveldown]: https://github.com/Level/leveldown
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[level]: https://github.com/Level/level
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[encoding-down]: https://github.com/Level/encoding-down
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