Use JavaScript objects as databases


Adds functions to Underscore/Lo-Dash for manipulating database-like objects.

It adds:

  • get
  • insert
  • update
  • updateWhere
  • remove
  • removeWhere
  • save
  • load
  • createId

Data can be persisted using the filesystem or localStorage.

Live example

For a full JSON database built on Lo-Dash and Underscore.db, check LowDB.


$ npm install underscore underscore.db
var _   = require('underscore');
var _db = require('underscore.db');


$ bower install underscore underscore.db
<script src="underscore.js" type="text/javascript"></script>
<script src="underscore.db.js" type="text/javascript"></script>

To use Underscore.db with Lo-Dash, just replace underscore with lodash

Create an empty database object

var db = {
  posts: []

Create a post

var newPost = _.insert(db.posts, {title: 'foo'});

Display database console.log(db)

  posts: [
    {title: "foo", id: "5ca959c4-b5ab-4336-aa65-8a197b6dd9cb"}

Retrieve post using underscore.db get or underscore find method

var post = _.get(db.posts, newPost.id);
var post = _.find(db.posts, function(post) {
  return post.title === 'foo'



The following database object is used in API examples.

var db = {
  posts: [
    {id: 1, body: 'one', published: false},
    {id: 2, body: 'two', published: true}
  comments: [
    {id: 1, body: 'foo', postId: 1},
    {id: 2, body: 'bar', postId: 2}

get(collection, id)

Finds and returns document by id or undefined.

var post = _.get(db.posts, 1);

insert(collection, document)

Adds document to collection, sets an id and returns created document.

var post = _.insert(db.posts, {body: 'New post'});

update(collection, id, attrs)

Finds document by id, copies properties to it and returns updated document or undefined.

var post = _.update(db.posts, 1, {body: 'Updated body'});

updateWhere(collection, whereAttrs, attrs)

Finds documents using _.where, updates documents and returns updated documents or an empty array.

// Publish all unpublished posts 
var posts = _.updateWhere(db.posts, {published: false}, {published: true});

remove(collection, id)

Removes document from collection and returns it or undefined.

var comment = _.remove(db.comments, 1);

removeWhere(collection, whereAttrs)

Removes documents from collection using _.where and returns removed documents or an empty array.

var comments = _.removeWhere(db.comments, {postId: 1});

save(db, [destination])

Persists database using localStorage or filesystem. If no destination is specified it will save to db or ./db.json.

_.save(db, '/some/path/db.json');


Loads database from localStorage or filesystem. If no source is specified it will load from db or ./db.json.

var db = _.load();
var db = _.load('/some/path/db.json');


Overwrite it if you want to use another id property.

_.id = '_id';

createId(collectionName, doc)

Called by Underscore.db when a document is inserted. Overwrite it if you want to change id generation algorithm.

_.createId = function(collectionNamedoc) {
  return collectionName + '-' + doc.name + '-' + _.random(1, 9999);

Everything you need for querying is present in Underscore and Lo-Dash: where, find, map, reduce, filter, reject, sortBy, groupBy, countBy, ...

See http://underscorejs.org/ or http://lodash.com/docs.


// Using Underscore 
var topFivePosts = _(db.posts)
  .where({published: true})
  .sortBy(function(post) {
     return post.views;
// Using Lo-Dash 
var topFivePosts = _(db.posts)
  .where({published: true})

With Lo-Dash, you can create optimal builds and include just what you need.

Minimal build for Underscore.db to work (~2kb min gzipped):

$ npm install -g lodash-cli
$ lodash underscore include=find,where,clone,indexOf

For more build options, see http://lodash.com/custom-builds.

Underscore.db is released under the MIT License.