koa-compose

What is koa-compose?

The koa-compose package is a middleware composition utility for Koa, a web framework for Node.js. It allows developers to combine multiple middleware functions into a single middleware without altering their signature. This is particularly useful for creating complex sequences of asynchronous operations that can be executed in a defined order.

What are koa-compose's main functionalities?

Middleware Composition

This feature allows the combination of multiple middleware functions into a single middleware chain. The code sample demonstrates how to compose two middleware functions and apply them to a Koa application.

const Koa = require('koa');
const compose = require('koa-compose');

const app = new Koa();

async function randomMiddleware(ctx, next) {
  // perform some operations
  await next();
}

async function anotherMiddleware(ctx, next) {
  // perform other operations
  await next();
}

const allMiddlewares = compose([randomMiddleware, anotherMiddleware]);

app.use(allMiddlewares);

app.listen(3000);

Other packages similar to koa-compose

connect

Connect is an extensible HTTP server framework for node using 'plugins' known as middleware. It is similar to koa-compose in the sense that it allows the use of middleware in a sequence. However, Connect is more of a server framework itself, whereas koa-compose is specifically designed for use with Koa.

express

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It has built-in middleware composition, similar to what koa-compose offers, but it is part of a larger framework rather than a standalone middleware utility.

redux

Redux is a state management library for JavaScript apps, and it features a 'compose' function that is conceptually similar to koa-compose. It allows for the composition of functions, particularly middleware in the context of Redux, to enhance store functionality. While it serves a different purpose (state management vs. HTTP middleware), the composition concept is a shared feature.

README

koa-compose

Compose middleware.

API

compose([a, b, c, ...])

Compose the given middleware and return middleware.

Debugging

To debug the interactions between middleware, you may use the DEBUG environment variable, for example:

$ DEBUG=koa-compose node --harmony app.js

When enabled this will output verbose response information and the middleware names to help visualize how they interact.

License

MIT