index.js

'use strict';

var dotenv = require('dotenv');
var fs = require('fs');

function difference (arrA, arrB) {
    return arrA.filter(function (a) {
        return arrB.indexOf(a) < 0;
    });
}

function compact (obj) {
    var result = {};
    Object.keys(obj).forEach(function (key) {
        if (obj[key]) {
            result[key] = obj[key];
        }
    });
    return result;
}

module.exports = {
    config: function (options) {
        options = options || {};
        options.silent = options.silent || !fs.existsSync('.env');

        // Original object that is parsed by dotenv.
        var parsedObj = dotenv.load(options);

        var sampleVars = dotenv.parse(fs.readFileSync(options.sample || '.env.example'));
        var allowEmptyValues = options.allowEmptyValues || false;
        var processEnv = allowEmptyValues ? process.env : compact(process.env);
        var missing = difference(Object.keys(sampleVars), Object.keys(processEnv));

        if (missing.length > 0) {
            throw new Error('Missing environment variables: ' + missing.join(', '));
        }

        // return original object or assemble from process.env
        return parsedObj
          ? parsedObj
          : Object.keys(sampleVars).reduce(function (acc, key) {
            acc[key] = process.env[key]
            return acc;
          }, {});
    },
    parse: dotenv.parse
};

module.exports.load = module.exports.config;