Hyper-console documentation

Hyperconsole screenshot



gem 'hyper-console'

To the development and test sections of your Gemfile.

Do a bundle install, and rm -rf tmp/cache, then restart the server, hit one of your web pages, and the console will open.

Note currently you must have enabled the Hyperloop::Application channel in your policies. Hopefully we can remove this in the future

Note for Rails 4.x you will also need to add these lines to config/initializer/assets.rb:

Rails.application.config.assets.precompile += %w( hyper-console-client.css )
Rails.application.config.assets.precompile += %w( hyper-console-client.min.js )


The hyper-console gem adds the console method to Kernel. If you call console from anywhere in your client code, it will open a new popup window, that is running an IRB style read-eval loop. The console window will compile what ever ruby code you type, and if it compiles, will send it to your main window for execution. The result (or error message) plus any console output will be displayed in the console window.

  • You may use the up/down arrow keys to move to previous expressions, edit them, and resend.
  • If you are editing a block of code you can send the block immediately without moving to the end of the expression by using command (or ctrl) enter.
  • The console history is stored in the popups html local store, so it will be retained across window reloads.
  • The expression can be arbitrarily complex. You can investigate model scopes, and attributes, run Operations, and get the current value of component states.
  • You can even create classes, or open existing classes and modify their behavior.

The instance method

The console gem adds an instance method to all classes. This will return an array like object of all the current instances of that class, except instances bound to closures (sorry!).

For example if you have a component named Components::TodoItem then

Components::TodoItem.instance[0] # first instance
Components::TodoItem.instance    # array of all the instances
Components::TodoItem.instance[0].dom_node  # returns the mount point

This is all very handy for investigating the state of Components and Stores. For example assuming your top level component is named App and is using hyper-router, you can do things like this:

App.instance[0].location.pathname # current path
App.instance[0].history.push '/topics' # change path to `/topics`

Because its common for there to be a single instance of some classes, the expression instance[0] can be shortened to just instance when there is only one instance of a class. For example in the above example you could just say App.instance.location.pathname.

Console Context

Each console window (you can have several) has an execution context, which is simply an expression that is used to determine the value of self that console executes in.

For example let's say you have a Todo model. You could in the console window evaluate

console context: 'Todo.first'

And a new console window will be opened that is "bound" to Todo.first so that in this window you can simply evaluate


Instead of Todo.first.title

Combining this with the instance method gives you a way to create a console window on a specific object in your application:

console context: 'App.instance'

Will create a console window whose self is your top level application component.

Note: if no context is provided, the context will be main opal context.

Console Titles

You can also give console windows a title:

console text: 'App.instance', title: 'App'

Loading / Reloading from Javascript

The hyperconsole method is added to the javascript window object, so in your application's javascript console you can say hyperconsole() to load (or reload) the main hyperconsole window. When reloading any prior command history will be retained, so this makes a nice escape hatch if things ever become totally confused.

Loading at Application Boot

By default a console will be created when your page loads. You can turn this off by setting ruby config.console_auto_start = false in your hyperloop rails initializer.

You can still start the console using hyperconsole() as described above.

How it works

The console and main application window communicate via two Hyperloop Operations: Evaluate, and Response.

As you type, the console runs the Opal compiler in the console window, and when you have a valid ruby expression, the resulting compiled code is sent to the main window using Evaluate. The main window receives the Evaluate dispatch, does a javascript eval and returns the result.


After checking out the repo, run bundle install.

The console assets are packaged into a single JS file, and a single style sheet. Running rake will build the packages, and put them in the appropriate directories.

TODO (help wanted)

  • configurable themes, especially smaller font size
  • full keyboard controls (i.e things like ctrl-a moves to beginning of line)
  • remove dependency on Hyperloop::Application channel
  • Peer to peer communication once initial connection is made
  • Chrome extension so that console can be attached physically to main window
  • add some kind of test suite, and ability to test without building the asset package