Koa Framework - Tuong-Nguyen/JavaScript-Structure GitHub Wiki

Features

• Minimal with Middlewares

  // Add a middleware
  app.use(async (ctx, next) => {
    ctx.body = 'Hello World!';
  });

- Call next to execute next middleware. Otherwise, it is not called.

• Future: async - await (ES8): no callback

async function foo() {
  const userId = 42;
  const user = await User.findById(userId);

  return user.name;
}

- await for waiting an asynchronous (async) function to return.
- try/catch is used for handling exception.

API References (http://koajs.com/)

• Application:
  • contains an array of middlewares which are cascading

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

// x-response-time
app.use(async function (ctx, next) {
  const start = new Date();
  await next();
  const ms = new Date() - start;
  ctx.set('X-Response-Time', `${ms}ms`);
});

// logger
app.use(async function (ctx, next) {
  const start = new Date();
  await next();
  const ms = new Date() - start;
  console.log(`${ctx.method} ${ctx.url} - ${ms}`);
});

// response
app.use(ctx => {
  ctx.body = 'Hello World';
});

app.listen(3000);

• Context: encapsulate request, response objects.
  • A context is created per request.
  • context.req: Node's request object
  • context.res: Node's response object
  • context.request: Koa's request object (abstraction of Node's request) provides additional functionality
  • context.response: Koa's response object (abstraction of Node's response) provides additional functionality
  • context.state: recommended namespace for passing information through middlewares and views

https://www.tutorialspoint.com/koajs/

Libraries

Middlewares

• koa-static
• koa-bodyparser
• koa-router
• koa-views: render html using different template engine.
• koa-session: Simple session middleware for Koa. default is cookie-based session and support external store.
• koa-mount: Mount other Koa applications as middleware.

Supported libraries

• nconf: Key-Value store which can load data from argv - env - file setting. (Preferred!)
• dotenv: allow us to define values in .env file and get them to process.env namespace
• Winston: node logger
• [koa-morgan]: Http logger which logs http request and response

Database

• mongodb-migration: tool & library for migrating mongo database which can be used in integration with database.
• koa-mongo