@types/koa-compose

What is @types/koa-compose?

@types/koa-compose provides TypeScript definitions for the koa-compose package, which is a middleware composition library for Koa.js. It allows you to compose multiple middleware functions into a single middleware function, making it easier to manage and organize your middleware stack.

What are @types/koa-compose's main functionalities?

Compose Middleware

This feature allows you to compose multiple middleware functions into a single middleware function. The composed middleware can then be used in a Koa application.

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

const middleware1 = async (ctx, next) => {
  console.log('Middleware 1');
  await next();
};

const middleware2 = async (ctx, next) => {
  console.log('Middleware 2');
  await next();
};

const composedMiddleware = compose([middleware1, middleware2]);

app.use(composedMiddleware);

app.listen(3000);

Error Handling in Middleware

This feature demonstrates how to handle errors in composed middleware. The errorHandler middleware catches any errors thrown by subsequent middleware and handles them appropriately.

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

const errorHandler = async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    ctx.status = err.status || 500;
    ctx.body = err.message;
    ctx.app.emit('error', err, ctx);
  }
};

const middleware = async (ctx, next) => {
  throw new Error('Something went wrong');
};

const composedMiddleware = compose([errorHandler, middleware]);

app.use(composedMiddleware);

app.listen(3000);

Other packages similar to @types/koa-compose

koa

Koa is a web framework for Node.js that provides a suite of methods for writing middleware. While koa-compose is specifically for composing middleware, Koa itself includes built-in support for middleware composition and other features for building web applications.

express

Express is another popular web framework for Node.js that uses a similar middleware pattern. While it does not use koa-compose, it has its own mechanism for composing middleware functions. Express is more feature-rich and has a larger ecosystem compared to Koa.

async

The async library provides utility functions for working with asynchronous JavaScript, including functions for composing asynchronous functions. While not specific to middleware, it can be used to achieve similar functionality in different contexts.

README

Installation

npm install --save @types/koa-compose

Summary

This package contains type definitions for koa-compose (https://github.com/koajs/compose).

Details

Files were exported from https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/koa-compose.

index.d.ts

import * as Koa from "koa";

declare function compose<T1, U1, T2, U2>(
    middleware: [Koa.Middleware<T1, U1>, Koa.Middleware<T2, U2>],
): Koa.Middleware<T1 & T2, U1 & U2>;

declare function compose<T1, U1, T2, U2, T3, U3>(
    middleware: [Koa.Middleware<T1, U1>, Koa.Middleware<T2, U2>, Koa.Middleware<T3, U3>],
): Koa.Middleware<T1 & T2 & T3, U1 & U2 & U3>;

declare function compose<T1, U1, T2, U2, T3, U3, T4, U4>(
    middleware: [Koa.Middleware<T1, U1>, Koa.Middleware<T2, U2>, Koa.Middleware<T3, U3>, Koa.Middleware<T4, U4>],
): Koa.Middleware<T1 & T2 & T3 & T4, U1 & U2 & U3 & U4>;

declare function compose<T1, U1, T2, U2, T3, U3, T4, U4, T5, U5>(
    middleware: [
        Koa.Middleware<T1, U1>,
        Koa.Middleware<T2, U2>,
        Koa.Middleware<T3, U3>,
        Koa.Middleware<T4, U4>,
        Koa.Middleware<T5, U5>,
    ],
): Koa.Middleware<T1 & T2 & T3 & T4 & T5, U1 & U2 & U3 & U4 & U5>;

declare function compose<T1, U1, T2, U2, T3, U3, T4, U4, T5, U5, T6, U6>(
    middleware: [
        Koa.Middleware<T1, U1>,
        Koa.Middleware<T2, U2>,
        Koa.Middleware<T3, U3>,
        Koa.Middleware<T4, U4>,
        Koa.Middleware<T5, U5>,
        Koa.Middleware<T6, U6>,
    ],
): Koa.Middleware<T1 & T2 & T3 & T4 & T5 & T6, U1 & U2 & U3 & U4 & U5 & U6>;

declare function compose<T1, U1, T2, U2, T3, U3, T4, U4, T5, U5, T6, U6, T7, U7>(
    middleware: [
        Koa.Middleware<T1, U1>,
        Koa.Middleware<T2, U2>,
        Koa.Middleware<T3, U3>,
        Koa.Middleware<T4, U4>,
        Koa.Middleware<T5, U5>,
        Koa.Middleware<T6, U6>,
        Koa.Middleware<T7, U7>,
    ],
): Koa.Middleware<T1 & T2 & T3 & T4 & T5 & T6 & T7, U1 & U2 & U3 & U4 & U5 & U6 & U7>;

declare function compose<T1, U1, T2, U2, T3, U3, T4, U4, T5, U5, T6, U6, T7, U7, T8, U8>(
    middleware: [
        Koa.Middleware<T1, U1>,
        Koa.Middleware<T2, U2>,
        Koa.Middleware<T3, U3>,
        Koa.Middleware<T4, U4>,
        Koa.Middleware<T5, U5>,
        Koa.Middleware<T6, U6>,
        Koa.Middleware<T7, U7>,
        Koa.Middleware<T8, U8>,
    ],
): Koa.Middleware<T1 & T2 & T3 & T4 & T5 & T6 & T7 & T8, U1 & U2 & U3 & U4 & U5 & U6 & U7 & U8>;

declare function compose<T>(middleware: Array<compose.Middleware<T>>): compose.ComposedMiddleware<T>;

declare namespace compose {
    type Middleware<T> = (context: T, next: Koa.Next) => any;
    type ComposedMiddleware<T> = (context: T, next?: Koa.Next) => Promise<void>;
}

export = compose;

Additional Details

• Last updated: Tue, 07 Nov 2023 09:09:38 GMT
• Dependencies: @types/koa

Credits

These definitions were written by jKey Lu, and Anton Astashov.