Bootloader

The bootloader provides a module(2) function that takes a module path and a module definition. The path is written in normal dot notation. module(2) will take care of setting things up and making sure nothing is accidentally overwritten.

The bootloader performs the following:

• Recursively iterate through the object
• Bind all functions to their immediate parent
• Collect all dependency declarations from a special attribute in each object named dependsOn, which is an array of absolute references to other modules in dot notation (e.g. ["x.y.z", "d.e"])
• Call all init functions in the prescribed order
• Remove all init functions from the structure to prevent repeated calls
• Also remove the dependsOn attribute after initialization

The bootloader itself is written in object-literal module style and expects the application to call module.init(1), which would execute the bootloader and bootstrap all registered modules. Note that calling module.init(1) would also remove that method according to the rules outlined above. This is by design as you should not initialize twice.

module.init(1) takes an optional object that is the parameter object. The same object is passed to every init function during initialization.

Note that you can simply call module(1) with just the path. It would return the object at that level without adding or modifying any property. For instance, calling module('a.b.c').d(); is the same as calling module.a.b.c.d(), which is the same as calling module().a.b.c.d().

Setup

Install Component.IO:

$ npm install -g component

To install, run in your repo:

$ component install pixbi/bootloader

To test:

$ npm install
$ npm test

Usage

Assume these modules:

module('pixbi.app', {
  dependsOn: ['pixbi.user'],

  initialized: '',

  init: function init () {
    this.initialized = 'triens';
    console.log('secundus');
  },

  isInit: function isInit () {
    console.log(this.initialized);
  }
});

module('pixbi.user', {
  init: function init () {
    console.log('primus');
  }
});

Running:

module.init();
module.pixbi.app.isInit.call(null);

would print to the console log:

primus
secundus
triens

Asynchronous Initialization

init functions can be either synchronous or asynchronous. If the bootloader detects that the init function takes an argument, like:

module('example', {
  init: function init (done) {
    // ...
    setTimeout(done, 1000);
  }
});

The above module will block all other modules that have a higher dependency score from loading for a second. Note that it does not mean that modules that depend on it, but modules who happen to have a higher score, which guarantees that its dependencies (but also some other unrelated modules) are blocked. This is due to the fact that we use a simple algorithm to calculate dependency scores (vs building a full-fledged dependency graph) to save on some space and cycles.

Copyright and License

Code and documentation copyright 2014 Pixbi. Code released under the MIT license. Docs released under Creative Commons.