Here's an overview of what this buildpack does:

• Uses the semver.io webservice to find the latest version of node that satisfies the engines.node semver range in your package.json.
• Allows any recent version of node to be used, including pre-release versions.
• Uses an S3 caching proxy of nodejs.org for faster downloads of the node binary.
• Discourages use of dangerous semver ranges like * and >0.10.
• Uses the version of npm that comes bundled with node.
• Puts node and npm on the PATH so they can be executed with heroku run.
• Caches the node_modules directory across builds for fast deploys.
• Doesn't use the cache if node_modules is checked into version control.
• Runs npm rebuild if node_modules is checked into version control.
• Always runs npm install (with devDependencies) to ensure npm script hooks are executed.
• Always runs npm prune after restoring cached modules to ensure cleanup of unused dependencies.

For more technical details, see the heavily-commented compile script.

Create a new app with this buildpack:

heroku create myapp --buildpack https://github.com/abecadel/heroku-buildpack-nodejs-grunt-bower.git

Or add this buildpack to your current app:

heroku config:add BUILDPACK_URL=https://github.com/abecadel/heroku-buildpack-nodejs-grunt-bower.git

Enable heroku user-env-compile lab:

heroku labs:enable user-env-compile

Set the NODE_ENV environment variable (e.g. development or production):

heroku config:set NODE_ENV=production

Push to heroku

git push heroku master
...
-----> Heroku receiving push
-----> Fetching custom buildpack... done
-----> Node.js app detected
-----> Resolving engine versions
       Using Node.js version: 0.8.2
       Using npm version: 1.1.41
-----> Fetching Node.js binaries
-----> Vendoring node into slug
-----> Installing dependencies with npm
       ...
       Dependencies installed
-----> Building runtime environment
-----> Found gruntfile, running grunt heroku task
Running "heroku" task
...
-----> Discovering process types

npm can be run with a verbose flag to help debugging if something fails when installing the dependencies.

• if the VERBOSE environment variable is set, npm is always run with verbose logging.
• if BUILDPACK_RETRY_VERBOSE is set, npm is relaunched in verbose mode if npm failed.

Thanks to mackwic for these extensions.

For more information about using Node.js and buildpacks on Heroku, see these Dev Center articles:

• Heroku Node.js Support
• Getting Started with Node.js on Heroku
• Buildpacks
• Buildpack API
• Grunt: a task-based command line build tool for JavaScript projects