App Compose

Create scalable, module-based applications with ease.

Motivation

Modern applications require a modular structure to ensure flexibility and adapt to business needs. Building a truly modular system inevitably brings the challenge of bringing all components together. In this process, it’s critical to manage the connection flow: loading one module first, then another, while controlling their dependencies. Complexity increases when it becomes necessary to disable parts of the system without leaving traces in the code (such as if/else statements) and without disrupting the operation of other components.

app-compose provides the ability not only to flexibly disable modules on demand but also to completely exclude their code from loading when they are turned off. Moreover, all dependencies of a disabled module are also automatically excluded, which helps save resources and maintain high application performance.

How does this library solve this problem?

Example

There are three entities: users, accounts, and wallets.

If the user exists, then the accounts entity should be started. If the accounts entity is done, then the wallets entity should be started.

import { createContainer, compose } from '@grlt-hub/app-compose';

// wrap the module in a container
const user = createContainer({
  id: 'user',
  start: async () => {
    const data = await fetchUser();

    return { api: { data } };
  },
});

const accounts = createContainer({
  id: 'accounts',
  dependsOn: [user],
  start: async ({ user }) => {
    const data = await fetchAccounts({ id: user.data.id });

    return { api: { data } };
  },
  enable: ({ user }) => user.data.id !== null,
});

const wallets = createContainer({
  id: 'wallets',
  dependsOn: [accounts],
  start: () => ({ api: null }),
});

// up the containers
await compose.up([user, wallets, accounts]);

// { user: 'idle',     accounts: 'idle',     wallets: 'idle' }
// { user: 'pending',  accounts: 'idle',     wallets: 'idle' }
// { user: 'done',     accounts: 'idle',     wallets: 'idle' }
//
/* if user.data.id !== null */
/** { user: 'done',    accounts: 'pending',  wallets: 'idle' } **/
/** { user: 'done',    accounts: 'done',     wallets: 'pending' } **/
/** { user: 'done',    accounts: 'done',     wallets: 'done' } **/
//
/* else */
/** { user: 'done',    accounts: 'off',      wallets: 'off' } **/
//
// compose.up done

The library offers convenient functions for creating and composing modules into a single system. Each module is encapsulated in a container with a clear configuration, including parameters like id, dependsOn, optionalDependsOn, start, and enable. Developers describe containers and launch them using compose.up fn, without the need to worry about the order of execution. This approach makes working with containers intuitive and close to natural language.

Strengths of the Library

• Provides a simple and intuitive developer experience (DX).
• Designed with a focus on quality and performance.
• Weighs less than 1.2 kB, making it lightweight.
• Covered by 100% tests, including type tests.
• Ensures high performance, suitable for scalable applications.
• Follows semantic versioning (semver), guaranteeing stability and predictability of changes with each release.

Documentation

For additional information, guides and api reference visit documentation site.