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This article mainly introduces the relevant knowledge of "how to use the Koa framework in Node.js". The editor shows you the operation process through an actual case. The method of operation is simple and fast, and it is practical. I hope this article "how to use the Koa framework in Node.js" can help you solve the problem.

Koa

Koa was born to solve some design defects of Express. Its middleware can be written through async function, and await next () can interrupt the execution of the middleware until all subsequent middleware has been executed, and then implement the onion model through await next ().

Another feature is the simplified handling of request and response, both of which are mounted on ctx, and the returned content can also be used by direct assignment, such as: ctx.response.body = fs.createStream ('really_large.xml').

And Koa cut off the routing function, it is realized through middleware, which is a minimalist idea of the micro-kernel.

Core functions (documentation for Koa):

More extreme request / response simplification than Express, such as:

Ctx.status = 200

Ctx.body = 'hello node'

Middleware implemented using async function.

Have the ability to "suspend execution".

It also fits the onion model in the case of asynchronism.

Simplify the kernel, and all the additional functions are moved to the middleware.

Koa revamped the game of rock scissors paper

Similarly, the code for the game.js game module and index.html page remains unchanged, so you need to install dependency packages: koa and koa-mount (npm i koa koa-mount)

Koa-mount can mount other applications as middleware, and the path parameters passed to the mount () function are temporarily stripped from the url until the stack is released. It is useful for creating an entire app or middleware that works well regardless of which path is used. It mounts the middleware to a specific path, and the middleware acts independently of this path.

Index.js code modification:

/ / load the module const fs = require ('fs'); const koa = require (' koa'); const mount = require ('koa-mount'); const game = require ('. / game'); let playerWon = 0; / / number of wins const app = new koa (); / / simplify the kernel, and all additional functions are moved to the middleware for implementation. Routing uses middleware implemented through mount / / mounts the middleware to a specific path through mount (), and the middleware acts independently of this path. / / favicon.ico path routing app.use (mount ('/ favicon.ico', function (ctx) {/ / a pair of `request` and `response`) is simplified, both of which are mounted on `ctx`, and the returned content can also be directly assigned to use ctx.status = 200; return }) / / multiple function middleware cannot be followed in mount, and can be mounted on koa through new koa (): const gameKoa = new koa (); app.use (mount ('/ game', gameKoa)) / / Separation module gameKoa.use (async function (ctx, next) {if (playerWon > = 3) {/ / response.status (500); / / response.send ('I won't play anymore!') / / use = assignment, which simplifies ctx.status = 500; ctx.body ='I won't play anymore!' ; return;} / / execute the subsequent middleware await next () through next; / / when the subsequent middleware is executed, it will be executed to this location if (ctx.playerWon) {playerWon++;}) / / you can use async function and await next () to execute asynchronous middleware in koa / / to make it conform to the onion model in the case of async. GameKoa.use (async function (ctx, next) {const query = ctx.query; const playerAction = query.action; if (! playerAction) {ctx.status = 400; return;} ctx.playerAction = playerAction; await next ();}) / / Asynchronous processing, gameKoa.use (async function (ctx, next) {const playerAction = ctx.playerAction; const result = game (playerAction) is returned after 500ms / / for operations that must be completed in the request main process, be sure to use await to wait / / otherwise koa will return http response to await new Promise in the current event loop (resolve = > {setTimeout () = > {ctx.status = 200) If (result = = 0) {ctx.body = 'draw'} else if (result =-1) {ctx.body = 'you lost'} else {ctx.body = 'you won' ctx.playerWon = true;} resolve () )) / / Open the page index.htmlapp.use (mount ('/', function (ctx) {ctx.body = fs.readFileSync (_ _ dirname +'/ index.html', 'utf-8') return;})) / / listening port 3000app.listen (3000); Express VS Koa

Express has a lower threshold and Koa is more powerful and elegant.

Express encapsulates more things, develops faster, and Koa is more customizable.

Which are they "superior" or "inferior"?

In fact, there is no difference between the advantages and disadvantages of the framework.

Different frameworks have different applicable scenarios.

This is the end of the content about "how to use the Koa framework in Node.js". Thank you for reading. If you want to know more about the industry, you can follow the industry information channel. The editor will update different knowledge points for you every day.

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