JavaScript dependency injection container example

DI.js

function argsList(method) {
    method = method.toString();
    const fn = /^function\s*[^\(]*\(\s*([^\)]*)\)/m;
    const cls = /constructor\s*[^\(]*\(\s*([^\)]*)\)/m;
    const FN_ARGS = method[0] === 'f' ? fn : cls;
    const depsStr = method.match(FN_ARGS);
    const deps = (depsStr) ? depsStr[1].trim().split(/[\s,]+/) : [''];

    if (deps[0] === '') {
        return [];
    }

    return deps;
}

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

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

    diContainer.register = function (name, instance) {
        dependencies[name] = instance;
    };

    diContainer.class = (name, ObjectClass) => {
        factories[name] = function () {
            const args = argsList(ObjectClass)
                .map(dependency => diContainer.get(dependency));

            return new ObjectClass(...args);
        };
    };

    diContainer.get = function (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 = function (factory) {
        const args = argsList(factory)
            .map(function (dependency) {
                return diContainer.get(dependency)
            });

        return factory.apply(null, args);
    };

    return diContainer;
};