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104 lines
3.8 KiB
104 lines
3.8 KiB
# MemDOWN [](http://travis-ci.org/Level/memdown) [](https://coveralls.io/github/Level/memdown?branch=master) [](https://www.npmjs.com/package/memdown) [](https://www.npmjs.com/package/memdown) |
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<img alt="LevelDB Logo" height="100" src="http://leveldb.org/img/logo.svg"> |
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A drop-in replacement for [LevelDOWN](https://github.com/rvagg/node-leveldown) that works in-memory. |
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Can be used as a backend for [LevelUP](https://github.com/rvagg/node-levelup) rather than an actual LevelDB store. |
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## Example |
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As of version 0.7, LevelUP allows you to pass a `'db'` option when you create a new instance. This will override the default LevelDOWN store with a LevelDOWN API compatible object. MemDOWN conforms exactly to the LevelDOWN API but only performs operations in memory, so your data is discarded when the process ends or you release a reference to the database. |
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```js |
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var levelup = require('levelup') |
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// note that if multiple instances point to the same location, |
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// the db will be shared, but only per process |
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, db = levelup('/some/location', { db: require('memdown') }) |
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db.put('name', 'Clint Eastwood') |
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db.put('dob', 'May 31, 1930') |
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db.put('occupation', 'Badass') |
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db.readStream() |
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.on('data', console.log) |
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.on('close', function () { console.log('Go ahead, make my day!') }) |
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``` |
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Note in this example we're not even bothering to use callbacks on our `.put()` methods even though they are async. We know that MemDOWN operates immediately so the data will go straight into the store. |
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Running our example gives: |
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``` |
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{ key: 'dob', value: 'May 31, 1930' } |
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{ key: 'name', value: 'Clint Eastwood' } |
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{ key: 'occupation', value: 'Badass' } |
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Go ahead, make my day! |
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``` |
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Global Store |
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--- |
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Even though it's in memory, the location parameter does do something. MemDOWN |
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has a global cache, which it uses to save databases by the path string. |
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So for instance if you create these two MemDOWNs: |
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```js |
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var db1 = levelup('foo', {db: require('memdown')}); |
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var db2 = levelup('foo', {db: require('memdown')}); |
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``` |
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...they will actually share the same data, because the `'foo'` string is the same. |
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You may clear this global store via the `MemDOWN.clearGlobalStore()` function: |
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```js |
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require('memdown').clearGlobalStore(); |
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``` |
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By default, it doesn't delete the store but replaces it with a new one, so the open instance of MemDOWN will not be affected. |
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`clearGlobalStore` takes a single parameter, which if truthy clears the store strictly by deleting each individual key: |
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```js |
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require('memdown').clearGlobalStore(true); // delete each individual key |
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``` |
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If you are using MemDOWN somewhere else while simultaneously clearing the global store in this way, then it may throw an error or cause unexpected results. |
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Browser support |
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---- |
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See [.zuul.yml](https://github.com/Level/memdown/blob/master/.zuul.yml) for the full list of browsers that are tested in CI. |
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But essentially, this module requires a valid ES5-capable browser, so if you're using one that's not ES5-capable (e.g. PhantomJS, Android < 4.4, IE < 10), then you will need [the es5-shim](https://github.com/es-shims/es5-shim). |
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Testing |
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---- |
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npm install |
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Then: |
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npm test |
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Or to test in the browser using Saucelabs: |
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npm run test-browser |
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Or to test locally in your browser of choice: |
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npm run test-browser-local |
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To run the linter: |
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npm run lint |
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To check code coverage: |
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npm run coverage |
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Licence |
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--- |
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MemDOWN is Copyright (c) 2013-2015 Rod Vagg [@rvagg](https://twitter.com/rvagg) and licensed under the MIT licence. All rights not explicitly granted in the MIT license are reserved. See the included LICENSE file for more details.
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