Override

Override is a general purpose middleware framework for Node.js that lets you override and extend built in functionality.

Override modules are executed in sequence before your main module is loaded, making it possible to run additional code on startup & modify built in prototypes and functions.

For example, Override modules make it possible to replace the built in console.log with a version that sends the logs to a third party service, chroot the current process, enable profiling etc. etc.

Installation

Install override as a global package (use sudo if you're on Ubuntu or Mac):

npm -g install override

Usage

To run your app via override replace the call to node with node-override passing in your Override environment before the filename of your main module. So instead of node index.js, use node-override -e or-mylog index.js (first install the or-mylog Override module with npm install or-mylog).

Environments

Override environments are simply comma separated lists of Override package or module names. You may for example have different environments for development, staging and production.

You can avoid specifying the environment every time you run your app by setting the OVERRIDE_ENV environment variable.

For example on *nix you can do this with:

export OVERRIDE_ENV=or-mylog,or-simple

Override Modules

Override modules have the following signature:

module.exports = function(next) {
  console.log('Hello Override!');
  next();
}

Here, the code outside of the exported function runs in a clean environment, before any overrides have had effect.

The exported function accepts a single parameter, which is the next function to call in the override middleware chain. The middleware chain terminates with the loading of the app's main module. As such any calls after next() will take place after the main module has been loaded.

Use environment variables to pass configuration parameters to your module. You can specify the names and types of configuration parameters required by your Override module in its package.json. For an example, check out or-timeout/package.json.

Override modules are distributed as packages via NPM. The convention is to prefix the name with or-. This makes it easy to search for them on http://search.npmjs.org. These existing open source modules make for great examples you can use as the basis for your own Override module.

License

(The MIT License)

Copyright (c) 2012+ Oleg Podsechin

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.