diContainer.js

/*
* A DI Container.
* */

"use strict";

const fnArgs = require('parse-fn-args');

module.exports = () => {
    const dependencies = {};
    const factories = {};
    const diContainer = {};

    diContainer.factory = (name, factory) => {
        factories[name] = factory;
    };

    diContainer.register = (name, dep) => {
        dependencies[name] = dep;
    };

    diContainer.get = (name) => {
        if (!dependencies[name]) {
            const factory = factories[name];
            dependencies[name] = factory &&
                diContainer.inject(factory);
            if (!dependencies[name]) {
                throw new Error('Cannot find module: ' + name);
            }
        }
        return dependencies[name];
    };

    diContainer.inject = (factory) => {
        const args = fnArgs(factory)
            .map(function (dependency) {
                return diContainer.get(dependency);
            });
        return factory.apply(null, args);
    };

    return diContainer;
};