Nodejs framework express and KOA

The framework is introduced

express The framework is based on Node.js Minimalism of the platform 、 agile web Application development framework , Based mainly on Connect middleware , And it encapsulates the route itself 、 View processing and other functions .

koa yes Express The original team is based on ES6 A framework for redevelopment of new features , Based mainly on co middleware , The framework itself does not contain any middleware , Many functions need to be solved with the help of third-party middleware , But because it's based on ES6 generator Asynchronous process control of features , It's solved “callback hell” And troublesome error handling problems .

The same thing

Both frames are correct http It was packaged . dependent api Almost. , Written by the same group .

Difference

express There are many built-in middleware available , and koa No, .

express Include routing , View rendering and other features , and koa Only http modular .

express The middleware model of is linear , and koa The middleware model is U type , It can also be called onion model construction middleware .

express Implement asynchronous functions through callbacks , In multiple callbacks 、 It is easy to write logic confusion in multiple middleware .

One 、 start ： Create a simple server

Native node

var http = require('http');

http.createServer(function (request, response) {
    

    //  send out  HTTP  Head  
    // HTTP  The status value : 200 : OK
    //  Content type : text/plain
    response.writeHead(200, {
    'Content-Type': 'text/plain'});

    //  Send response data  "Hello World"
    response.end('Hello World\n');
}).listen(8888);

//  The terminal prints the following information 
console.log('Server running at http://127.0.0.1:8888/');
// or 
const app=http.createServer()
app.on('request',(req,res)=>{
    })

express

//express_demo.js  file 
var express = require('express');
var app = express();
 
app.get('/', function (req, res) {
    
   res.send('Hello World');
})
 
var server = app.listen(8081, function () {
    
 
  var host = server.address().address
  var port = server.address().port
 
  console.log(" Application example , The visiting address is  http://%s:%s", host, port)
 
})

koa

//  Import koa, and koa 1.x Different , stay koa2 in , What we import is a class, So in capital Koa Express :
const Koa = require('koa');

//  Create a Koa Objects represent web app In itself :
const app = new Koa();

//  For any request ,app This asynchronous function will be called to process the request ：
app.use(async (ctx, next) => {
    
    await next();
    ctx.response.type = 'text/html';
    ctx.response.body = '<h1>Hello, koa2!</h1>';
});

//  In the port 3000 monitor :
app.listen(3000);
console.log('app started at port 3000...');

Two 、 Requests and responses

express

app.get('/', function (req, res) {
    
   // request  and  response  Object to process request and response data 
})

koa
Parameters ctx By koa The incoming package request and response The variable of , We can visit through it request and response,next yes koa The next asynchronous function passed in to be processed .

async (ctx, next) => {
    
    await next();
    //  Set up response Of Content-Type:
    ctx.response.type = 'text/html';
    //  Set up response The content of :
    ctx.response.body = '<h1>Hello, koa2!</h1>';
}

3、 ... and 、 route

Native node

var server = require("./server");
var router = require("./router");
 
server.use(router.route);

express

// GET  request 
app.get('/', function (req, res) {
    
   console.log(" Home page  GET  request ");
   res.send('Hello GET');
}) 
// POST  request 
app.post('/', function (req, res) {
    
   console.log(" Home page  POST  request ");
   res.send('Hello POST');
})

koa

// GET  request   How to write it 1：
app.use(async (ctx, next) => {
    
    if (ctx.request.path === '/') {
    
        ctx.response.body = 'index page';
    } else {
    
        await next();
    }
});
// GET  request   How to write it 2：
const Koa = require('koa');
const router = require('koa-router')();//  Be careful require('koa-router') It returns a function :
const app = new Koa();

// add url-route:
router.get('/hello/:name', async (ctx, next) => {
    
    var name = ctx.params.name;
    ctx.response.body = `<h1>Hello, ${
      name}!</h1>`;
});

router.get('/', async (ctx, next) => {
    
    ctx.response.body = '<h1>Index</h1>';
});

// add router middleware:
app.use(router.routes());

app.listen(3000);
console.log('app started at port 3000...');

Four 、 Static files

express

// Express  Provides built-in middleware  express.static  To set static files such as ：img, CSS, JavaScript  etc. .
app.use('/public', express.static('public'));

koa

//  Method 1 ： Write a processing method by yourself 
let staticFiles = require('./static-files');
app.use(staticFiles('/static/', __dirname + '/static'));

//  Method 2 ： Introduce a package 
const Koa = require('koa');
const app = new Koa();
const bodyParser = require('koa-bodyparser');
const Router = require('koa-router');
const router = new Router();
const render = require('koa-ejs');
const path = require('path');
const serve = require('koa-static');
app.use(bodyParser());

/** Static resources （ Server side ） */
app.use(serve(path.join(__dirname + "/public")));

//  initialization ejs, Set the suffix to html, The file directory is `views`
render(app, {
    
    root: path.join(__dirname, 'views'),
    layout: false,
    viewExt: 'html',
    cache: false,
    debug: false
});
//  monitor 3000 port 
app.listen(3000);

5、 ... and 、get\post Method of transmitting and receiving parameters

Native node

// get 
var http = require('http');
var url = require('url');
var util = require('util');
 
http.createServer(function(req, res){
    
    res.writeHead(200, {
    'Content-Type': 'text/plain'});
 
    //  analysis  url  Parameters 
    var params = url.parse(req.url, true).query;
    res.write(" The websites ：" + params.name);
    res.write("\n");
    res.write(" Website  URL：" + params.url);
    res.end();
 
}).listen(3000);
// post
var http = require('http');
var querystring = require('querystring');

http.createServer(function (req, res) {
    
  var body = "";
  req.on('data', function (chunk) {
    
    body += chunk;
  });
  req.on('end', function () {
    
    //  Analytical parameters 
    body = querystring.parse(body);
    //  Set response header information and code 
    res.writeHead(200, {
    'Content-Type': 'text/html; charset=utf8'});
 
    if(body.name && body.url) {
     //  Output submitted data 
        res.write(" The websites ：" + body.name);
        res.write("<br>");
        res.write(" Website  URL：" + body.url);
    } else {
      //  Output form 
        res.write(postHTML);
    }
    res.end();
  });
}).listen(3000);

express
get Method of transmitting and receiving parameters

app.get('/process_get', function (req, res) {
    
 
   //  Output  JSON  Format 
   var response = {
    
       "first_name":req.query.first_name,
       "last_name":req.query.last_name
   };
   console.log(response);
   res.end(JSON.stringify(response));
})

post Method of transmitting and receiving parameters

app.post('/process_post', urlencodedParser, function (req, res) {
    
 
   //  Output  JSON  Format 
   var response = {
    
       "first_name":req.body.first_name,
       "last_name":req.body.last_name
   };
   console.log(response);
   res.end(JSON.stringify(response));
})

koa

// POST
const bodyParser = require('koa-bodyparser');
router.post('/signin', async (ctx, next) => {
    
    var
        name = ctx.request.body.name || '',
        password = ctx.request.body.password || '';
    console.log(`signin with name: ${
      name}, password: ${
      password}`);
    if (name === 'koa' && password === '12345') {
    
        ctx.response.body = `<h1>Welcome, ${
      name}!</h1>`;
    } else {
    
        ctx.response.body = `<h1>Login failed!</h1> <p><a href="/">Try again</a></p>`;
    }
});
app.use(bodyParser());

6、 ... and 、cookie management

express
Use middleware to Node.js Server send cookie Information

// express_cookie.js  file 
var express = require('express')
var cookieParser = require('cookie-parser')
var util = require('util');
 
var app = express()
app.use(cookieParser())
 
app.get('/', function(req, res) {
    
    console.log("Cookies: " + util.inspect(req.cookies));
})
 
app.listen(8081)

Here are some awesome , Written by the great God Egg.js And Koa：https://eggjs.org/zh-cn/intro/egg-and-koa.html