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A tiny & fast key value store with append-only disk log. Ideal for apps with < 1 million records.


npm install dirty

Why dirty?

This module is called dirty because:

  • The file format is newline separated JSON
  • Your database lives in the same process as your application, they share memory
  • There is no query language, you just forEach through all records

So dirty means that you will hit a very hard wall with this database after ~1 million records, but it is a wonderful solution for anything smaller than that.


  var Dirty = require('dirty');
  var db = new Dirty('user.db');

  db.on('load', function() {
    db.set('john', {eyes: 'blue'});
    console.log('Added john, he has %s eyes.', db.get('john').eyes);

    db.set('bob', {eyes: 'brown'}, function() {
      console.log('User bob is now saved on disk.')

    db.forEach(function(key, val) {
      console.log('Found key: %s, val: %j', key, val);

  db.on('drain', function() {
    console.log('All records are saved on disk now.');


Added john, he has blue eyes.
Found key: john, val: {"eyes":"blue"}
Found key: bob, val: {"eyes":"brown"}
User bob is now saved on disk.
All records are saved on disk now.


new Dirty([path])

Creates a new dirty database. If path does not exist yet, it is created. You can also omit the path if you don't want disk persistence (useful for testing).


The path of the dirty database.

dirty.set(key, value, [cb])

Set's the given key / val pair. The state of the database is affected instantly, the optional cb callback is fired when the record was written to disk.

val can be any JSON-serializable type, it does not have to be an object.


Retrieves the value for the given key.

dirty.rm(key, cb)

Removes the record with the given key. This is identical to setting the key's value to undefined.

dirty.update(key, updater, [cb])

Updates the record of the given key with the given updater which is a function that is passed the current value of the key.

The optional cb callback is passed to dirty.set.


Calls the given fn function for every document in the database. The passed arguments are key and val. You can return false to abort a query (useful if you are only interested in a limited number of records).

This function is blocking and runs at ~4 Mhz.


Close the dirty db file handle.

dirty event: 'load' (length)

Emitted once the database file has finished loading. It is not safe to access records before this event fires. Writing records however should be fine.

length is the amount of records the database is holding. This only counts each key once, even if it had been overwritten.

You can chain the on load to the contructor as follows:

var db = dirty(file).on('load', function() { ... });

dirty event: 'drain' ()

Emitted whenever all records have been written to disk.

dirty event: 'read_close' ()

Emitted once the database file read stream closed.

dirty event : 'write_close' ()

Emitted once the database file write stream closed.


Build Status

Dirty utilizes the Mocha test framework.

git clone
cd node-dirty
npm install
npm test


node-dirty is licensed under the MIT license.


A tiny & fast key value store with append-only disk log. Ideal for apps with < 1 million records.







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