useit

A readable method to load and initialize a module and use it everywhere.

Motivation

As is well known a large Node application is structured in some (or a lot!) of small modules. Some of this modules may require an initial configuration like this:

// load module
var mod = require('a module');
// initialize it
mod.init(args);

// the module is now initialized

When you need to use the module already initialized into another module, you need only to require it into the other module, because Node do not load it again, but gets the previous cached module:

// this is into another module of the same application
var mod = require('a module');

// the module is already initialized

If the required module does not have a dedicated init method but exports only a function to use for the initialization, like in this case:

var intiMod = require('a module')(args);

// the module is now initialized

you need to access initMod from another module. Do to this you can use another module to store all shared variables or use the Node global namespace or use this simple loader (see below).

Usage

// instead to use this
var intiMod = require('a module')(arg1, arg2, arg3, ...);

// use this
var useit = require('useit');
var intiMod = useit.load('a module').init(arg1, arg2, arg3, ...);

// use initMod

Now into all other modules you can simply use initMod:

var useit = require('useit');
var intiMod = useit.use('a module');

// use initMod

Another way is this:

var useit = require('useit');
var intiMod = useit.load('./file-with-full-path').as('myModule').init(arg1, arg2, arg3, ...);

// use initMod

and use it into another module:

var useit = require('useit');
var intiMod = useit.myModule;

// use initMod

The latest method is also useful if you want to manage a flat global list of modules (with or without initialization needs):

var useit = require('useit');
var firstModule = useit.load('./first-file-with-full-path').as('first').init(args);
var secondModule = useit.load('./second-file-with-full-path').as('second').init(args);

and use them into another module:

var useit = require('useit');
var firstModule = useit.first;
var secondModule = useit.second;

The follow method is equivalent to previous:

var useit = require('useit');
var firstModule = useit.use('first');
var secondModule = useit.use('second');

You can use also a relative path. In the following example, if you have a node application with this structure:

/app/
    /lib/
        file1.js
        file2.js
        loader.js
index.js

you can load all files from loader script:

// content of loader.js:
var useit = require('useit');
var firstModule = useit.load('./file1').as('first').init(args);
var secondModule = useit.load('./file2').as('second').init(args);

Since the 1.2.0 version of useit is possible to load a previous required module:

var useit = require('useit');
var someModule = require('some-module');
var firstModule = useit.load(someModule).as('first').init(args);

In all other modules you can use the initialized module:

var useit = require('useit');
var firstModule = useit.first;

Since the 1.3.0 version is possible to load a previous initialized module without reinitialize it:

var useit = require('useit');
var someModule = require('some-module')(opts);
var firstModule = useit.load(someModule).as('first').init();

In all other modules you can use the initialized module:

var useit = require('useit');
var firstModule = useit.first;

NOTE Only a module that exports a function is allowed.

Since the 1.4.0 version is possible to add a function as an alert called before use a configuration:

var useit = require('useit');
var someModule = require('some-module')(opts);
var firstModule = useit
  .load(someModule)
  .as('first')
  .alert(function () {
    if (this.testProperty !== 'value') {
      throw new Error('wrong value');
    }
  })
  .init();

var recallModule = useit.first; // throws an error if recallModule.testProperty !== 'value'

The alert function is executed in the context of the loaded module.

Installation

Install useit as usual:

$ npm install useit

Tests

As usual our tests are written in the BDD styles for the Mocha test runner using the should assertion interface and the best coverage tool Blanket. To run the test simply type in your terminal:

$ npm test

To run the coverage test type instead:

$ npm run cov

License

Copyright (c) 2014 Yoovant by Marcello Gesmundo. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
• Neither the name of Yoovant nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.