Generic configuration parser for my Node.js projects. Allows to override selectively with environment variables.

conf.example.js

module.exports = {
    key1: 'foo',
    key2: {
        subkey1: 'foo',
        subkey2: {
            subsubkey1: 'foo',
            // ...
        }
    }
}

confParser.js

// Generic configuration parser for my Node.js projects.
//
// https://gist.github.com/EyalAr/3bc1c209f3d10c70692d
//
// Allows to override selectively with environment variables.

// Your configuration will be overridden by environment variables if:
// 1. [envPrefix]_ENV_OVERRIDE is set
// or:
// 2. [envPrefix]_ENV is set and not 'development'
//
// Environment variables structure:
// conf.key1 ==> MY_APP_KEY1
// conf.key1.subkey2 ==> MY_APP_KEY1_SUBKEY2
// conf.key1.subkey2.subsubkey3 ==> MY_APP_KEY1_SUBKEY2_SUBSUBKEY3

module.exports = function(envPrefix, confFile) {
    var resolve = require('path').resolve,
        conf = require(resolve(process.cwd(), confFile)),
        res = {};

    // override with environment variables if:
    // 1. [envPrefix]_ENV_OVERRIDE is set
    // or:
    // 2. [envPrefix]_ENV is set and not 'development'
    var envOverride = !!process.env[envPrefix + '_ENV_OVERRIDE'] || (process.env[envPrefix + '_ENV'] && process.env[envPrefix + '_ENV'] !== 'development');
    if (!envOverride) return conf;
    traverse(conf, []);
    return res;

    function setVal(obj, path, val) {
        var first = path.shift();
        if (path.length === 0) return obj[first] = val;
        if (typeof obj[first] !== 'object') obj[first] = {};
        setVal(obj[first], path, val);
    }

    function traverse(obj, path) {
        Object.keys(obj).forEach(function(key) {
            var val = obj[key],
                kPath = [key];
            Array.prototype.unshift.apply(kPath, path);
            if (typeof val !== 'object') {
                // corresponding environment variable:
                var eVar = (envPrefix + '_' + kPath.join('_')).toUpperCase();
                // override if defined
                if (process.env[eVar]) {
                    console.log('Conf: Using env var', eVar);
                    val = process.env[eVar];
                }
                setVal(res, kPath, val);
            } else {
                traverse(val, kPath);
            }
        });
    }
}

example.js

// let's say the following env vars are set:
// MY_APPY_ENV=staging
// MY_APP_KEY1=bar

var confParser = require('./confParser'),
    conf = confParser('MY_APP', './conf.example.js');
    
// conf.key1 === 'bar'
// conf.key2.subkey1 === 'foo'
// conf.key2.subkey2.subsubkey1 === 'foo'