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#Introduction

Hem is a project for compiling CommonJS modules when building JavaScript web applications. You can think of Hem as Bundler for Node, or Stitch on steroids.

This is rather awesome, as it means you don't need to faff around with coping around JavaScript files. jQuery can be a npm dependency, so can jQueryUI and all your custom components. Hem will resolve dependencies dynamically, bundling them together into one file to be served up. Upon deployment, you can serialize your application to disk and serve it statically.

Hem was primarily designed for developing Spine.js based Single Page Web Applications (SPA's), so a major role it fills is to tie up some of the other lose ends of a frontend development project - things like running tests, precompiling code, and preparing it for deployment. It can even help out in the API connection stuff if your app needs that.

#Installation

npm install -g hem

or

npm install -g git://github.com/spine/hem.git

or ...fun trick.

hem install -g hem 
git clone https://github.com/spine/hem.git
cd hem
npm link

this last approach is great if you want to customize hem for your own use, (...or for developing npm packages in general). Just fork and use you own path!

##Dependencies

Hem has two types of dependency resolutions: Node modules and Stitch modules.

Node modules: Hem will recursively resolve any external Node modules your code references. This means that Spine, jQuery etc, can all be external Node modules - you don't have lots of libraries floating around your application. This also has the advantage of explicit versioning; you'll have much more control over external libraries.

Stitch modules: Hem will bundle up your whole application (without any static dependency analysis), automatically converting CoffeeScript (.coffee), Jade templates (.jade) and Eco templates (.eco or .jeco). Hem doesn't use static analysis of your application to determine dependencies, as that's often not-viable considering the amount of dynamically loaded dependencies most applications use.

In a nutshell, Hem will make sure your application and all its dependencies are wrapped up in a single file, ready to be served to web browsers.

##CommonJS

CommonJS modules are at the core of Hem, and are the format Hem aspects every module to adhere to. As well as ensuring your code is encapsulated and modular, CommonJS modules give you dependency management, scope isolation, and namespacing. They should be used in any JavaScript application that spans more than a few files.

To find out more about why CommonJS modules are a great solution to JavaScript dependency management, see the CommonJS guide

It's not that AMD pattern is bad by the way, just not the way hem went for now.

###The Format

The format is remarkably straightforward, but is something you'll have to adhere to in every file to make it work. CommonJS uses explicit exporting; so to expose a property inside a module to other modules, you'll need to do something like this:

In app/controllers/users.coffee:

class Users extends Spine.Controller

Explicitly export the Users object

module.exports = Users

The format mandates that a module object will be available in every module. However, if you're targeting both the CommonJS format, and a normal environment, you can do a conditional export, checking that the module object exists.

module?.exports = Users

###Requiring modules

Requiring other modules is just as straightforward; just use the require() function.

Users = require("controllers/users")

In Hem apps, all module paths are relative to the app folder - so don't require files relative to the specific module. CSS

##Styling your app

Hem will also bundle up all your application's CSS into one file, ready to serve up to clients. CSS encapsulation and modularity is just as important as JavaScript de-coupling (and can get as equally messy if it's not done right); Hem goes some way to help you with this. To compile CSS, Hem uses an excellent library called Stylus. Stylus is mostly a superset of CSS, and the normal CSS syntax will work just fine if that's all you want.

However the awesome part of Stylus is the extra syntactical sugar it brings to CSS. Features like optional braces and colons, mixins, variables and significant whitespace all vastly improve your application's CSS, and decreases the amount of typing necessary. In a nutshell, Stylus is to CSS as CoffeeScript is to JavaScript.

Stylus files are indicated by the .styl extension, and are automatically compiled down to CSS by Hem. This all happens in the background, so you don't need to worry about it.

Also in the pipeline is the ability to bundle up CSS from Node modules.

##slug.json

Hem has some good defaults (convention over configuration), but sometimes you'll need to change them, especially when adding libraries and dependencies.

For configuration, Hem uses a slug.json file, located in the root of your application. Hem expects a certain directory structure. A main JavaScript/CoffeeScript file under app/index, a main CSS/Stylus file under css/index and a public directory to serve static assets from. If you're using Spine.app, these will all be generated for you.

Hem also allows you to specify static JavaScript libraries to include, under the "libs" option:

{
  "libs": [
    "./lib/other.js"
  ]
}

These will be included before the rest of your JavaScript, and without being wrapped in the CommonJS module transport format. In addition, Hem lets you specify an array of npm/Node dependencies, to be included in your application. For example, in a default generated Spine.app slug.json file, you'll find the following dependencies:

{
  "dependencies": [
    "es5-shimify",
    "json2ify",
    "jqueryify",
    "jquery.tmpl",
    "spine"
  ]
}

These dependencies will be statically analyzed, to recursively resolve additional dependencies, and then wrapped in the CommonJS module format, being served up with the rest of your application's JavaScript. In other words, you don't have to have jquery.js, spine.js and json2.js floating around inside your application, they can be Node modules, installed through npm.

##Usage

Ok, so now we've looked at how to configure Hem, let's actually use it in an application. As I mentioned earlier, this step is much easier with an application previously generated by Spine.app, and I advise you go down this route if you're unfamiliar with Hem.

Now, we can start a development server, which will dynamically build our application every request, using the server command:

hem server

By default, your spine application is served at http://localhost:9294. You can configure the host and port from command line or as settings in your package.json

hem server -p 9295 --host 192.168.1.1 -d

Would result in your application being served in debug mode at http://192.168.1.1:9295/

If there's an index.html file under public, it'll be served up. Likewise, any calls to /application.js and /application.css will return the relevant JavaScript and CSS.

For the sake of avoiding cross domain issues in development environments when your spine app is utilizing an ajax api there is a optional proxy server built into hem. Including the following in your slug.json configures that:

"useProxy": true,
"baseSpinePath": "/apiapp/spineapp/",
"baseApiPath": "/apiapp/",
"apiHost": "localhost",
"apiPort": 8080,
"proxyPort": 8001,

now http://localhost:8001/apiapp/spineapp/ will return the spine app.

and http://localhost:8001/apiapp/ will return your apiApp

so relative links like @url = "../api/album/" from inside your spine app can resolve against your apiApp without issue

When you're ready to deploy, you should build your application, serializing it to disk.

hem build

This will ensure that your server can statically serve your application, without having to use Node, or have any npm dependencies installed.

TODO: hem build should have an option to version the js/css it producess and replace the references in index.html as well

hem build -setVersion -version 24

###Views

Currently Hem supports three template options out of the box

  • Straigt HTML - stringifed html... that you can render...
  • Eco - erb like syntax, like ejs, but with coffeeScript. Nice, but seems to be a somewhat abandoned project
  • Jade - haml like syntax with optional coffeescript filter
    • to use jade templates you must include jades runtime.js as a lib in your spine projects slug.json "libs": ["lib/runtime.js"],

Note: hem > 0.2 dropped support for jquery templates (.tmpl) as it is an abandoned project for quite some time

We are looking into ways to inject custom compilers down then road.

###Testing

Testacular is a neat little tool that we leverage with hem.

hem test

Will run tests in a spine projects test directory. Tests can be written in CoffeeScript!

hem watch -t

Will run tests as test files are updated. Testacular makes it smart. Only previously failing tests run. If there were no previously failing tests all will run. Default is to run tests in a new Chrome window. Firefox, Phantom or some others can be used as well.

hem server

will watch and compile jasmine tests, but you will have to go to localhost:9294/test (or whereever you configured hem to run...) and manually trigger page tests to run.

#TODO

  • Better document Testacular usage instructions.
  • Major restructure of slug.json. Much more customizeable in how hem outputs packages and what directory structure it expects. (coming in Hem 3!)
  • This would be cool -> integrate with live-reload for changes. We should be able to inject live-reload while in server mode and then run the livereload-server inside hem or could strata handle the incoming requests? Looks like simple json requests. Would we need an option for the browser to regain its focus? Another option is instead of injecting the script into the page is to use the live reload plugin.
  • Make hem more generic to work with other types of frameworks like angular?? probably move more configuration to slug.json if we do this
    • actually with more generic projects out there like yeoman maybe Hem should aim to be a dedicated spine dev tool.
  • Option to version generated js and css output when building (good for long cache optimization)
  • Auto build a cache.manifest file

#History

Originally developed by @maccman to compliment Spine.js. He started a replacement project which is a Ruby based project called Catapult. Some of us still love the node.js and Hem way of doing things. In the spirit of open source Hem advanced in a fork and a couple of us who use it at work plan to maintain for the near future at least.