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Gon gem — get your Rails variables in your js

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Gon. You should try this. If you look closer - you will see an elephant.

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If you need to send some data to your js files and you don't want to do this with long way through views and parsing - use this force!

Now you can easily renew data in your variables through ajax with!

With Jbuilder, Rabl, and Rabl-Rails support!

For Sinatra available gon-sinatra.

For .Net MVC available port NGon.

Sponsored by Evil Martians

An example of typical use

Very good and detailed example and reasons to use is considered in railscast by Ryan Bates

When you need to send some start data from your controller to your js you might be doing something like this:

  1. Write this data in controller(presenter/model) to some variable
  2. In view for this action you put this variable to some objects by data attributes, or write js right in view
  3. Then there can be two ways in js:
    • if you previously wrote data in data attributes - you should parse this attributes and write data to some js variable.
    • if you wrote js right in view (many frontenders would shame you for that) - you just use data from this js - OK.
  4. You can use your data in your js

And everytime when you need to send some data from action to js you do this.

With gon you configure it firstly - just put in layout one tag, and add gem line to your Gemfile and do the following:

  1. Write variables by

    gon.variable_name = variable_value
    # or new syntax
      :user_id => 1,
      :user_role => "admin"
    gon.push(any_object) # any_object with respond_to? :each_pair
  2. In your js you get this by

  3. profit?

With the feature you can easily renew data in gon variables! Simply call from your js file. It's super useful in modern web applications!


More details about configuration and usage you can find in gon wiki


  <title>some title</title>
  <%= Gon::Base.render_data %>
  <!-- include your action js code -->

For rails 3:

  <%= include_gon %>

You can pass some options to render_data method.

You put something like this in the action of your controller:

@your_int = 123
@your_array = [1,2]
@your_hash = {'a' => 1, 'b' => 2}
gon.your_int = @your_int
gon.your_other_int = 345 + gon.your_int
gon.your_array = @your_array
gon.your_array << gon.your_int
gon.your_hash = @your_hash

gon.all_variables # > {:your_int => 123, :your_other_int => 468, :your_array => [1, 2, 123], :your_hash => {'a' => 1, 'b' => 2}}
gon.your_array # > [1, 2, 123]

# gon.clear # gon.all_variables now is {}

Access the variables from your JavaScript file:


AMD compatible version: include_gon_amd

If your site uses AMD modules you can use the include_gon_amd helper to include the variables and watch function as a module. Options are mostly the same as for include_gon, except for namespace_check, which does nothing and namespace, which is used as the name of the defined module. The end result will look somewhat like the following:

define('yourNameSpace', [], function() {
  var gon = {};
  gon.yourVariable = yourValue;
  // etc...

  return gon;

A (very) simplified usage example:


include_gon_amd namespace: 'data'

Some JavaScript module

define(['data'], function(data) {
}); - renew your data easily!

You can use gon for renewing your data without reloading pages and writing long js functions! It's really great for some live values.

Supports and usage.

Instruction for usage

Usage with Rabl

You can write your variables assign logic to templates with Rabl. The way of writing Rabl templates is very clearly described in their repo.

Profit of using Rabl with gon:

  1. You can clean your controllers now!
  2. Work with database objects and collections clearly and easyly
  3. All power of Rabl
  4. You can still be lazy and don't use common way to transfer data in js
  5. And so on

Instruction for usage gon with Rabl.

Usage with Rabl-Rails

gon.rabl works with rabl-rails. Learn to write RABL the rabl-rails way here.

Add gon and rabl-rails to your environment:

gem 'gon'
gem 'rabl-rails'

Define a rabl template using rabl-rails syntax:

object :@user
attributes :id, :name, :email, :location

Call gon.rabl in your controller

def show
  @user = User.find(params[:id])

Usage with Jbuilder

Use gon with Jbuilder as with Rabl:

Instruction for usage gon with Jbuilder.

You can use gon for sending your data to js from anywhere! It's really great for some init data.

Instruction for usage

Speed up Gon

You can use any JSON Engine you want. Gon uses MultiJson with autodetect mode, so all you need is just require your JSON library.


  • @gazay
  • @takiy33

Special thanks to @brainopia, @kossnocorp and @ai.


The MIT License