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Collaboratively edit and synchronize JSON-style data with Node.js
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Collaboratively edit JSON-style data in realtime using Socket.IO by synchronizing all operations on a planetary shared object. Each operation will be received in exactly the same order as they are incoming to the Planet server. This includes the client that is emitting the operation. This approach guarantees the exact same state on all clients and has been proven to work reliably in other projects such as netpd.

Planet is optimized to edit JSON style data and does not require OT. If you are looking for rich text editing have a look at ShareJS.


  • operation - The custom events that can be used to modify the planetary shared object.

  • value - Can be of type string, number, object, array, boolean or null.

  • location - Is a property specified by a key (string) or path (array).

  • path - A path is an array of strings to specify a property in an object. Additinally a path can contain numbers to refer to an element within an array.

  • data - Refers always to an object.

  • state - The current content of the planet that can be manipulated by the operations or read with get.


  • set - Sets a value at a specific location. The value will be overwritten and not be merged.

  • remove - Deletes a value at specified location.

  • merge - Recursively merges data into the state.

  • delete - Deletes the state.

  • get - Asynchronously fetches values from the state, optionally at a specified location. Returns the whole state if no location is passed.


Arrays are not treated as objects and will not be merged by merge operations. The elements of an array can be set or fetched by get opernations. Removing single elements from an array is not yet specified.


Single characters of a string value can be manipulated with set or read with get.


npm install planet



var planet = require('planet'),
    socket = require('').listen(8080);

new planet(socket);


.on('connect', function(){
    this.emit('merge', {
        'sugar': 1,
        'milk': 0

    this.emit('set', 'sugar', 2);
    this.emit('set', 'milk', 100);

    this.emit('get', function(data){
        // {'sugar': 2, 'milk': 100}

Include the Client

<script src="//localhost:8080/"></script>
// or within Node.js 
var io = require('');

Client API

Method: connect

var earth = io.connect('//:8004', options);
  1. URI (string)
  2. Options (object) - the configuration object.

Method: disconnect


Method: on

Adds a listener for planet operations: set, remove, merge, delete, get and the Socket.IO Client Events.

Method: once

Adds a one time listener, which is removed after the first time the event is fired.

Method: emit

Emits the following Planet operations: set, remove, merge, delete, get.

Emit: set

earth.emit('set', 'bag', null); // {'bag': null}
earth.emit('set', 'bag', {'sugar': 20}); // {'bag': {'sugar': 20}}
earth.emit('set', ['bag', 'eggs'], 12); // {'bag': {'sugar': 20, 'eggs': 12}}
earth.emit('set', ['todo-list', 0], 'My first thing todo');

Emit: remove

earth.emit('remove', 'key');
earth.emit('remove', ['bag', 'eggs']);

Emit: merge

earth.emit('merge', {'bag': {'eggs': 6, 'milk': 100}});
earth.emit('merge', {'bag': {'sugar': 20}});

Emit: delete


Emit: get

earth.emit('get', function(data){ });
earth.emit('get', 'bag', function(value){ });
earth.emit('get', ['bag', 'eggs'], function(value){ });
earth.emit('get', ['todo-list', 0], function(value){ });

Server API

Requires a Socket.IO socket.

var Planet = require('planet'),
    socket = require('').listen(8080, 'localhost');

Constructor: Planet

var earth = new Planet(socket, options);

The new keyword is optional.

  1. Socket - socket server.
  2. Options (object) - the configuration object.
  • limit - the maximum amount of concurent client connections. Defaults to 200.

Method: on

Adds a listener for Planet operations: set, remove, merge, delete, get. See also the standard Socket.IO Server Events.

Method: once

Adds a one time listener, which is removed after the first time the event is fired.

Method: merge

earth.merge({'key': 'value'});

Method: set

earth.set('bag', {'sugar': 20});
earth.set(['bag', 'eggs'], 12);
earth.set(['todo-list', 0], 'My first thing todo');

Method: remove

earth.remove(['bag', 'eggs']);

Method: delete


Method: get

earth.get(function(data){ });
earth.get('bag', function(value){ });
earth.get(['bag', 'eggs'], function(value){ });
earth.get(['todo-list', 0], function(value){ });

Planet Operations

Operations are fired as Socket.IO custom events on both the server and the client side.

Event: set

earth.on('set', function(key, value){ });
  1. Key (string or array) - the location to set a value.
  2. Value (string, number, object, array, boolean, null).

Event: remove

earth.on('remove', function(key){ });
  1. Key (string or array) - the location to delete.

Event: merge

earth.on('merge', function(data){ });
  1. Data (object) - the object to merge into the current state.

Event: delete

earth.on('delete', function(){ });


To run Planet form a command-line interface install Planet globally npm install planet -g or cd bin && ./planet.

CLI Options

  • -p, --port [NUMBER] - The port to bind to (default: 8004).

  • --host [STRING] - The host to connect to (default:

  • -l, --limit [NUMBER] - Maximum concurrent client connections, a number lower than your ulimit (default: 200).

  • -h, --help - Shows this help message.


Running tests requires the installation of Testigo.

git submodule update --init --recursive

node tests/run.js


node --stack_size=8192 planet # prevents exceeding maximum call stack size

Set ulimit -n 1024 if you want to connect with more than 200 clients.

node bench/run.js


  • Strict (option for disallowing auto-creation of setting keys at new location)
  • Predefined model (option for predefining a data structure and disalow merging/setting inexistent keys)
  • Latency optimization
  • Cleanup error messages
  • Eventually use instead of optparse
  • Eventually provide a client side script for merge, get and set manipulation


Dev Dependencies

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