mr

Montage Require

This is a CommonJS module system, highly compatible with NodeJS, intended for front-end development of web applications using NPM style packages. It is designed to be automatically replaced by the Montage Optimizer with a smaller, faster, and bundled production module system.

To use, install the module system in your application package with NPM.

npm install mr

Then, incorporate the Montage Require bootstrapping script in an HTML document.

<script
    src="node_modules/mr/bootstrap.js"
    data-module="index"
></script>

<script
    src="node_modules/mr/bootstrap.js"
    data-auto-package
    data-module="index"
></script>

<script
    src="node_modules/mr/bootstrap.js"
    data-package="."
    data-module="index"
></script>

• data-auto-package indicates that there is no package.json for this application, and instructs Montage Require to pretend that an empty one exists in the same directory as the HTML document.
• data-package alternately, indicates that there is a package.json and that it can be found at the given location. The default location is the same directory as the HTML file.
• data-module instructs Montage Require to require the given module after it has finished bootstrapping and the DOM content has loaded.

Node and NPM Compatibility

Montage fully supports CommonJS Modules and Packages. It also supports some of the extensions from NodeJS and NPM.

• module.exports: Modules that do not have cyclic dependencies (modules with dependencies that in turn ultimately depend their own exports) can redefine their exports object by assigning to module.exports.
• dependencies: If a package declares a package dependency using NPM’s dependencies property, Montage looks for that package in the package’s node_modules subdirectory. Montage Require also supports the case where a package with the same name is already loaded by a parent package. Unlike NPM, with Montage packages, you can override the location of the node_modules directory with the directories.packages property, or use mappings to find individual packages in alternate locations or give them different local names.

Extensions:

• redirects: a redirects block in package.json a module identifier to redirect to an alternate module identifier.
• returnable exports: A module can return an exports object. This would make that module incompatible with NodeJS, where the idiom module.exports = prevails.
• mappings: Packages can declare some or all of their package dependencies with the URL location of the package, particularly a URL relative to the depending package. Mappings override dependencies if there are conflicts.
• require.packageDescription: Packages expose the parsed contents of the package.json file.
• module.location: Packages expose the URL of the corresponding source.
• module.directory: Packages expose the URL of the directory containing the corresponding source.

Not supported:

• dependencies version predicates are ignored.
• __filename and __dirname are not injected into module scope. Consider using module.location and module.directory URLs instead.
• index.js is not sought if you require a directory. To make a package using an index.js compatible with Montage Require, add a redirects block to package.json like {"redirects": {"foo": "foo/index"}}.

The Montage modules debug-mode run-time loads modules asynchronously and calculates their transitive dependencies heuristically—by statically scanning for require calls using a simple regular expression. Montage can load cross-origin scripts in debug-mode if the CORS headers are set on the remote server.

Take a look at the Montage Optimizer to optimize applications for production. The optimizer can bundle packages with all of the dependent modules, can preload bundles of progressive enhancements in phases, and can generate HTML5 application cache manifests.

Cross-browser Compatibility

At present, Montage Require depends on document.querySelector and probably several other recent EcmaScript methods that might not be available in legacy browsers. With your help, I intend to isolate and fix these bugs.

At time of writing, tests pass in Chrome 21, Safari 5.1.5, and Firefox 13 on Mac OS 10.6.

Optimizer Options

The Montage Optimizer, mop, does not yet handle stand-alone Montage Require. However, when it does, the optimizer can convert entire packages to production ready versions without manual alteration. The optimizer rewrites HTML, particularly replacing the bootstrapping script with a bundle. As such, the run-time supports some additional options.

• data-bootstrap indicates that this script element is the bootstrap.js script and denotes the location of that script. This is normally inferred from being a script with a bootstrap.js file name, but an optimizer might replace the <script> tag with a bundle with a different name.

The optimizer can convert all resources into script-injection form, by changing .js modules to .load.js scripts with define(hash, id, descriptor) boilerplate. This permits packages to be loaded cross-origin and with content security policies that forbid eval. The hash is a consistent hash for each package. The bootstrapper needs to know these hashes so it can recognize incoming package.json.load.js definitions.

• data-bootstrap-hash
• data-application-hash
• data-q-hash

Among other things, the optimizer is also responsible for processing package.json files to include the hash of each dependency.

Maintenance

Tests are in the spec directory. All of the CommonJS module tests exist in there as well as tests for packaging and extensions.

Open spec/run.html in a browser to verify the specs.

This implementation is a part from Motorola Mobility’s Montage web application framework. The module system was written by Tom Robinson and Kris Kowal. Motorola holds the copyright on much of the original content, and provided it as open source under the permissive BSD 3-Clause license. This project is maintained by Kris Kowal, continuing with that license.