Node Cookbook - Third Edition by David Mark Clements & Matthias Buus & Matteo Collina & Peter Elger

Author:David Mark Clements & Matthias Buus & Matteo Collina & Peter Elger [Clements, David Mark]
Language: eng
Format: azw3
Tags: COM060160 - COMPUTERS / Web / Web Programming, COM021050 - COMPUTERS / Databases / Servers, COM051260 - COMPUTERS / Programming Languages / JavaScript
Publisher: Packt Publishing
Published: 2017-07-31T04:00:00+00:00

There's more...

Let's explore more Koa functionality.

Creating middleware

Let's copy the app folder from our main recipe to the custom-middleware-app and create a middleware folder with an answer.js file:

$ cp -fr app custom-middleware-app $ cd custom-middleware-app $ mkdir middleware $ touch middleware/answer.js

Our middleware/answer.js file should look like the following:

module.exports = answer function answer () { return async (ctx, next) => { ctx.set('X-Answer', 42) await next() }) }

In our main index.js file we can load our answer middleware like so:

const answer = require('./middleware/answer')

And then register the middleware with Koa as follows:

app.use(answer())

Our answer function returns an async function, which sets our custom header using ctx.set and then delegates execution to subsequent middleware by calling next with await (await next()).

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