Build koa server framework from 0 to 1

The difference between koa framework and express

express:
Contains a complete application framework with functions such as routing and templates, and takes up a lot of space
.
Koa : Koa module is a middleware core with higher modularity, small memory footprint, and fast running

Build express framework from 0 to 1

Initialize pakage.json

npm init

Installation dependencies
Paste the following code into pakage.json and execute npm install

"koa": "^2.13.1",
"koa-bodyparser": "^4.3.0",
"koa-onerror": "^4.1.0",
"koa-router": "^10.0.0",
"koa-static": "^5.0.0"

New app.js

const Koa = require('koa')//引入koa中间件
const app = new Koa()
const onerror = require('koa-onerror'); //异常记录
const fs = require('fs');

//设置路由中间件
app.use(async (ctx, next) => {
    
    
  await next()
});
//处理post方法接收到的数据
app.use(require('koa-bodyparser')());

//异常处理
onerror(app);

// 建立路由文件
const index = require('./router/index')
app.use(index.routes(), index.allowedMethods());

//设置静态目录
app.use(require('koa-static')(__dirname + '/public'));

// 异常处理
app.on('error', (err, ctx) => {
    
    
	ctx.res.writeHead(200,{
    
    
		'content-Type':'application/json'
	});
	ctx.res.end(JSON.stringify(err));
});

app.listen(3001);

Create a new route folder in the root directory

const koaRouter = require('koa-router');
const router = koaRouter();
//处理get请求
router.get('/oindex', async (ctx, next) => {
    
    
	let code="222"
	let msg="成功"
	let data={
    
    name:'111',status:"成功"}
	ctx.body={
    
    
		code,
		msg,
		data
	}
});
//处理post请求
router.post('/index', async (ctx, next) => {
    
    
	let code="222"
	let msg="成功"
	let data={
    
    name:'111',status:"成功"}
	ctx.body=ctx
	//返回异常
	// const error = new Error()
	//  error.code = 10000
	//  error.msg = '无此用户'
	// throw(error);
});

module.exports = router

Create a new veiw and template file index.html folder under veiw in the root directory

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>123</title>
	</head>
	<body>
		<p>hello</p>
	</body>
</html>

Final table of contents The

simple framework is completed! Post-login/request header processing/return to unified format/database link/login mechanism processing continue to add

Use koa-generator to quickly build

npm install koa-generator -g

koa project name

success! Just install the dependency and run it.
Pay attention to
the app.js configuration built with the framework (it is said to be an upgraded version)

//中间件配置时app.js
app.use(function *(next){
    
    
  var start = new Date;
  yield next;
  var ms = new Date - start;
  console.log('%s %s - %s', this.method, this.url, ms);
});
//使用时 router中
router.get('/', function *(next) {
    
    
  this.body = 'this is a users response!';
});

The online query configuration is basically

//中间件配置时app.js
app.use(async (ctx, next) => {
    
    
  await next()
});
//使用时 router中
router.post('/index', async (ctx, next) => {
    
    
	ctx.body=ctx
}）

After checking for a long time, the interface part will not be processed. Later, it is found that this in the framework is the ctx
framework configuration. The modification is changed to:

//中间件配置时app.js
app.use(function *(next){
    
    
  yield next;
 });
//使用时 router中
router.get('/', function *(next) {
    
    
  this.body = 'this is a users response!';
});

About ctx

https://koa.bootcss.com/
https://blog.csdn.net/weixin_43392420/article/details/85676384 Add link description