r42

r42

Mix in node's require, some angular dependency injection look&feel and the ease of use of RequireJS and what do you get?

Dependency injection done right for Node.js!

WARNING

This library is a work in progress. It won't have anything stable before 0.1.0. Please use with care. Right now, even small version changes can (and probably will) break your code.

Getting started

Installation

npm install r42

Your first module

Let's code lib/toto.js :

// path & fs are examples to show you how to load node modules
// _ will contain lodash (see next section to see why)
define(function (path, fs, _, dep1, dep2) {
  /* Your code goes here */

  // You can export anything, a scalar, a function, an object, an array...
  // Objects & functions should be preferred
  return /* what you exports goes here */;
});

Configuring & lauching your project

var r42 = require('r42');
var path = require('path');

r42.config({
  // Sets the root directory in which modules are looked for
  baseDir: path.join(__dirname, 'lib'),

  // Allows to map paths / module names to something else
  paths: {
    // _ will load lodash
    _: 'lodash',

    // Target paths are all relative to baseDir.
    // Here "library" will try to load "baseDir + '../vendor/library'"
    library: '../vendor/library',

    // Replacement in paths are also possible: here all modules named
    // 'sub/.../truc' will be looked for into the ../sub folder
    sub: '../sub',

    // Alias can also be used in configuration but they HAVE TO be declared
    // BEFORE being used in the object
    shMod: 'sh/module', // refers to 'sh/module'
    sh: 'shortcut',
    shMod2: 'sh/module2', // refers to 'shortcut/module2'
  },
});

// Let's get started
r42.inject(function (toto) {
  // you can use your dependency here
});

More complex dependencies

Module in subfolders

If you want to resolve complex names in subdirectories, you can use the optional replacer argument of the define function. Here is an example:

define({
  test: 'sub/folder/test',
}, function (test) {
  // here test will be resolved to module 'sub/folder/test'
});

The object maps an argument's name to the real module name locally. The argument name will be replaced by the given module name before injection happens.

You can also use special r42 comments (looking like /*! module */) before your argument names:

define(function (/*! sub/folder/test */ test) {
  // here test will be resolved to module 'sub/folder/test'
});

Note : spaces are optional in r42 comments.

Modules in the same folder

Sometimes, it is a pain to refer to a module in the same folder as you are right now. r42 allows for a fine way to do so.

Using $ to prefix your variable's name will automatically cause r42 to replace it by your current module's "path". It also works to prefix files in the replacer object.

In a module module/toto.js:

define({
  superSub: '$super/sub',
}, function (superSub, $sideFn, /*! $sub/sideValue */ sideVal) {
  // superSub refers to 'module/super/sub'
  // $sideFn refers to module/sideFn
  // sideVal refers to $sub/sideValue
});

Special case : index.js in a subfolder

You can refer to an index module using only the folder's name just like so:

In file folder/index.js:

define(function () {
  return {
    answer: 42
  };
});

And in a file at the same level as folder:

define(function ($folder) {
  // Here $folder will load folder/index.js
});

Circular dependencies

Those are working "automatically" but you NEED to exports barebone objects on both modules for it to work.

Here is an example:

In a module a.js:

define(function (b) {
  // here b might be empty if it was loaded before a, so don't use it

  return {
    aFn: function () {
      // here b should be fully usable
      b.bFn();
    },
  };
});

In a module b.js:

define(function (a) {
  // here a might be empty if it was loaded before b, so don't use it

  return {
    bFn: function () {
      // here a should be fully usable
      a.bFn();
    },
  };
});

Special APIs

Loading modules dynamically

You can also use r42.inject to load modules dynamically. In this case, provide a module name or module list and optionally a replacer as usual. Here is what it could look like:

In module dynamic.js

define(function (r42) {
  // This will load lodash in variable _.
  var _ = r42.inject('lodash');
  // Same thing for the variable alias but using the replacer argument.
  var alias = r42.inject({ alias: 'lodash' }, 'alias');

  // An example with multiple load at once
  // Here modules[0] will resolve to require('util')
  // and modules[1] to require('net')
  var modules = r42.inject(['util', 'net']);

  // You can also use the replacer argument with an array:
  // this example will load the same modules as the previous one
  modules = r42.inject({a: 'util', b: 'net'}, ['a', 'b']);
});

Printing dependencies

Right now, even if the output is rather horrible, it might give some useful information so here is how to use it:

BEWARE: This really can go away in between versions right now, maybe replaced by something achieving the same purpose but better designed. Don't use this for other purposes than debugging.

This function does not print modules handled by NPM right now.

var r42 = require('r42');

r42.config({
  // Your config HERE
});

// Let's get started
r42.inject(function (/* Your dependencies */) {
  // Dump dependencies using console.log
  r42.dumpDeps();
});

Using r42 in libraries

Since version 0.0.21, r42 has been rewritten to be completely synchronous. This means that you can use it easily, even to create library packages. Here is a simple example of what your main library file might look like :

var r42 = require('r42');
r42.config(/* Your configuration object */);

r42.inject(function (/* Your dependencies */) {
  module.exports = {
    // Whatever
  };
});