Use handlebars.js templates with the asset pipeline and sprockets

Are your handlebars.js templates littering your Rails views with script tags? Wondering why the nifty Rails 3.1 asset pipeline streamlines all your JavaScript except for your Handlebars templates? Wouldn't it be nice to have your Handlebars templates compiled, compressed, and cached like your other JavaScript?

Yea, I think so too. That is why I wrote handlebars_assets. Give your Handlebars templates their own files (including partials) and have them compiled, compressed, and cached as part of the Rails 3.1 asset pipeline!

Using sprockets with Sinatra or another framework? handlebars_assets works outside of Rails too (as of v0.2.0)

BREAKING CHANGE AS OF v0.9.0

My pull request to allow / in partials was pulled into Handlebars. The hack that converted partial names to underscored paths (shared/_time -> _shared_time) is no longer necessary and has been removed. You should change all the partial references in your app when upgrading from a version prior to v0.9.0.

Version of handlebars.js

handlebars_assets is packaged with an 1.0.0-rc4 of handlebars.js. See the section on using another version if that does not work for you.

Installation with Rails 3.1+

Load handlebars_assets in your Gemfile as part of the assets group

group :assets do
  gem 'handlebars_assets'
end

Installation without Rails 3.1+

handlebars_assets can work with earlier versions of Rails or other frameworks like Sinatra.

Load handlebars_assets in your Gemfile

gem 'handlebars_assets'

Add the HandlebarsAssets.path to your Sprockets::Environment instance. This lets Sprockets know where the Handlebars JavaScript files are and is required for the next steps to work.

env = Sprockets::Environment.new

require 'handlebars_assets'
env.append_path HandlebarsAssets.path

Compiling your JavaScript templates in the Rails asset pipeline

Require handlebars.runtime.js in your JavaScript manifest (i.e. application.js)

//= require handlebars.runtime

If you need to compile your JavaScript templates in the browser as well, you should instead require handlebars.js (which is significantly larger)

//= require handlebars

Precompiling

handlebars_assets also works when you are precompiling your assets.

rake assets:precompile

If you are using rake assets:precompile, you have to re-run the rake command to rebuild any changed templates. See the Rails guide for more details.

Heroku

If you are deploying to Heroku, be sure to read the Rails guide and in your config/application.rb set:

config.assets.initialize_on_precompile = false

This avoids running your initializers when compiling assets (see the guide for why you would want that).

However, that does mean that you cannot set your configuration in an initializer. This issue has a workaround, or you can set:

config.assets.initialize_on_precompile = true

This will run all your initializers before precompiling assets.

Templates directory

You should locate your templates with your other assets, for example app/assets/javascripts/templates. In your JavaScript manifest file, use require_tree to pull in the templates

//= require_tree ./templates

The template file

Write your Handlebars templates as standalone files in your templates directory. Organize the templates similarly to Rails views.

For example, if you have new, edit, and show templates for a Contact model

templates/
  contacts/
    new.hbs
    edit.hbs
    show.hbs

Your file extensions tell the asset pipeline how to process the file. Use .hbs to compile the template with Handlebars.

If your file is templates/contacts/new.hbs, the asset pipeline will generate JavaScript code

1. Compile the Handlebars template to JavaScript code
2. Add the template code to the HandlebarsTemplates global under the name contacts/new

You can then invoke the resulting template in your application's JavaScript

HandlebarsTemplates['contacts/new'](context);

The template namespace

By default, the global JavaScript object that holds the compiled templates is HandlebarsTemplates, but it can be easily renamed. Another common template namespace is JST. Just change the template_namespace configuration option when you initialize your application.

HandlebarsAssets::Config.template_namespace = 'JST'

Ember

To compile your templates for use with Ember.js simply turn on the config option

HandlebarsAssets::Config.ember = true

.hamlbars and .slimbars

If you name your templates with the extension .hamlbars, you can use Haml syntax for your markup! Use HandlebarsAssets::Config.haml_options to pass custom options to the Haml rendering engine.

For example, if you have a file widget.hamlbars that looks like this:

%h1 {{title}}
%p {{body}}

The Haml will be pre-processed so that the Handlebars template is basically this:

<h1> {{title}} </h1>
<p> {{body}} </p>

The same applies to .slimbars and the Slim gem. Use HandlebarsAssets::Config.slim_options to pass custom options to the Slim rendering engine.

Partials

If you begin the name of the template with an underscore, it will be recognized as a partial. You can invoke partials inside a template using the Handlebars partial syntax:

Invoke a {{> path/to/_partial }}

Using another version of handlebars.js

Occasionally you might need to use a version of handlebars.js other than the included version. You can set the compiler_path and compiler options to use a custom version of handlebars.js.

HandlebarsAssets::Config.compiler = 'my_handlebars.js' # Change the name of the compiler file
HandlebarsAssets::Config.compiler_path = Rails.root.join('app/assets/javascripts') # Change the location of the compiler file

Patching handlebars.js

If you need specific customizations to the handlebars.js compiler, you can use patch the compiler with your own JavaScript patches.

The patch file(s) are concatenated with the handlebars.js file before compiling. Take a look at the test for details.

HandlebarsAssets::Config.patch_files = 'my_patch.js'
HandlebarsAssets::Config.patch_path = Rails.root.join('app/assets/javascripts') # Defaults to `Config.compiler_path`

Thanks

This gem is standing on the shoulders of giants.

Thank you Yehuda Katz (@wycats) for handlebars.js and lots of other code I use every day.

Thank you Charles Lowell (@cowboyd) for therubyracer and handlebars.rb.

Author

Hi, I'm Les Hill and I make things go.

Follow me on Github and Twitter.

Contributors

• Matt Burke (@spraints) : execjs support

•                (@kendagriff)     : 1.8.7 compatibility
  

• Thorben Schröder (@walski) : 3.1 asset group for precompile
• Erwan Barrier (@erwanb) : Support for plain sprockets
• Brendan Loudermilk (@bloudermilk) : HandlebarsAssets.path
• Dan Evans (@danevans) : Rails 2 support
• Ben Woosley (@empact) : Update to handlebars.js 1.0.0.beta.6

•                (@cw-moshe)       : Remove 'templates/' from names
  

• Spike Brehm (@spikebrehm) : Config.template_namespace option
• Ken Mayer (@kmayer) : Quick fix for template_namespace option
• Brad Murray (@wyaeld) : Generic options support
• Blake Williams (@BlakeWilliams) : .handlebars extension
• Tristan Koch (@trkoch) : Strip leading whitespace from compiled templates
• Brian Cardarella (@bcardarella) : Ember support
• David Lee (@davidlee) : Slim support
• Phil Cohen (@phlipper) : README cleanup
• Akshay Rawat (@akshayrawat) : Update to handlebars.js 1.0.0-rc.3
• Turadg Aleahmad (@turadg) : Update to handlebars 1.0.0-rc.4
• Mark Rushakoff (@mark-rushakoff) : Synchronize Sprockets engine registers with Rails
• Alex Riedler (@AlexRiedler) : Pass scope and locals up the chain

Contributing

Pull requests are welcome! Please do not update the version number.

In a nutshell:

1. Fork
2. Create a topic branch - git checkout -b my_branch
3. Push to your branch - git push origin my_branch
4. Create a Pull Request from your branch
5. That's it!