express-pouchdb

An Express submodule with a CouchDB style REST interface to PouchDB.

Introduction

The express-pouchdb module is a fully qualified Express application with routing defined to mimic most of the CouchDB REST API, and whose behavior is handled by PouchDB. The intention is for express-pouchdb to be mounted into other Express apps for extended usability. A simple example of this is pouchdb-server, which is primarily used as a quick-and-dirty drop-in replacement for CouchDB in Node.js.

Screencasts

• Modular web applications with Node.js and Express

Installation

$ npm install express-pouchdb

Example Usage

Here's a sample Express app, which we'll name app.js.

var express = require('express'),
    app     = express(),
    PouchDB = require('pouchdb');

app.use('/db', require('express-pouchdb')(PouchDB));

app.listen(3000);

Now we can run this little guy and find each of express-pouchdb's routes at the /db prefix.

$ node app.js &
$ curl http://localhost:3000/db/
GET / 200 56 - 7 ms
{
  "express-pouchdb": "Welcome!",
  "version": "0.2.0"
}

Note: express-pouchdb conflicts with some middleware. You can work around this by only enabling affected middleware for routes not handled by express-pouchdb. body-parser is the most important middleware known to be problematic.

API

express-pouchdb exports a single function that builds an express application object. Its function signature is:

require('express-pouchdb')([PouchDB[, options]])

• PouchDB: the PouchDB object used to access databases. Optional.
• options: Optional. These options are supported:
• configPath: a path to the configuration file to use. Defaults to './config.json'.
• mode: determines which parts of the HTTP API express-pouchdb offers are enabled. There are three values:
  • 'fullCouchDB': enables every part of the HTTP API, which makes express-pouchdb very close to a full CouchDB replacement. This is the default.
  • 'minimumForPouchDB': just exposes parts of the HTTP API that map 1-1 to the PouchDB api. This is the minimum required to make the PouchDB test suite run, and a nice start when you just need an HTTP API to replicate with.
  • 'custom': no parts of the HTTP API are enabled. You can add parts yourself using the opts.overrideMode discussed below.
• overrideMode: Sometimes the preprogrammed modes are insufficient for your needs, or you chose the 'custom' mode. In that case, you can set this to an object. This object can have the following properties:
  • 'include': a javascript array that specifies parts to include on top of the ones specified by opts.mode. Optional.
  • 'exclude': a javascript array that specifies parts to exclude from the ones specified by opts.mode. Optional.

The application object returned contains some extra properties that offer additional functionality compared to an ordinary express application:

• setPouchDB: a function that allows changing the PouchDB object express-pouchdb uses on the fly. Takes one argument: the new PouchDB object to use.
• couchConfig: an object that provides programmatic access to the configuration file and HTTP API express-pouchdb offers. For an overview of available configuration options, take a look at Fauxton's configuration page. (/_utils#_config)
• couchLogger: an object that provides programmatic access to the log file and HTTP API express-pouchdb offers.

Examples

Example 1

Builds an HTTP API that exposes a minimal HTTP interface, but adds Fauxton as a debugging tool.

var app = require('express-pouchdb')({
  mode: 'minimumForPouchDB',
  overrideMode: {
    include: ['fauxton']
  }
});
// when not specifying PouchDB as an argument to the main function, you
// need to specify it like this before requests are routed to ``app``
app.setPouchDB(require('pouchdb'));

Example 2

builds a full HTTP API but excludes express-pouchdb's authentication logic (say, because it interferes with custom authentication logic used in our own express app):

var app2 = require('express-pouchdb')(require('pouchdb'), {
  mode: 'fullCouchDB' // specified for clarity. It's the default so not necessary.
  overrideMode: {
    exclude: [
      'routes/authentication',
      // disabling the above, gives error messages which require you to disable the
      // following parts too. Which makes sense since they depend on it.
      'routes/authorization',
      'routes/session'
    ]
  }
});

Using your own PouchDB

Since you pass in the PouchDB that you would like to use with express-pouchb, you can drop express-pouchdb into an existing Node-based PouchDB application and get all the benefits of the HTTP interface without having to change your code.

var express = require('express')
  , app     = express()
  , PouchDB = require('pouchdb');

app.use('/db', require('express-pouchdb')(PouchDB));

var myPouch = new PouchDB('foo');

// myPouch is now modifiable in your own code, and it's also
// available via HTTP at /db/foo

PouchDB defaults

When you use your own PouchDB code in tandem with express-pouchdb, the PouchDB.defaults() API can be very convenient for specifying some default settings for how PouchDB databases are created.

For instance, if you want to use an in-memory MemDOWN-backed pouch, you can simply do:

var InMemPouchDB = PouchDB.defaults({db: require('memdown')});

app.use('/db', require('express-pouchdb')(InMemPouchDB));

var myPouch = new InMemPouchDB('foo');

Similarly, if you want to place all database files in a folder other than the pwd, you can do:

var TempPouchDB = PouchDB.defaults({prefix: '/tmp/my-temp-pouch/'});

app.use('/db', require('express-pouchdb')(TempPouchDB));

var myPouch = new TempPouchDB('foo');

If you want express-pouchdb to proxy requests to another CouchDB-style HTTP API, you can use http-pouchdb:

var TempPouchDB = require('http-pouchdb')(PouchDB, 'http://localhost:5984');
app.use('/db', require('express-pouchdb')(TempPouchDB));

Functionality

On top of the exposing everything PouchDB offers through a CouchDB-like interface, express-pouchdb also offers the following extra functionality found in CouchDB but not in PouchDB by default (depending on the mode used, of course):

• Fauxton, a web interface for the HTTP API.
• Authentication and authorisation support. HTTP basic authentication and cookie authentication are available. Authorisation is handled by validation functions and security documents.
• Configuration support. You can modify configuration values manually in the config.json file, or use the HTTP or Fauxton interface.
• Replicator database support. This allows your replications to persist past a restart of your application.
• Support for show, list and update functions. These allow you to serve non-json content straight from your database.
• Rewrite and Virtual Host support, for nicer urls.

Contributors

If you want to become one of our wonderful contributors then check out the contributing guide!

License

The MIT License. See the LICENSE file for more information.