Express server development

Introduction to Express:

Let's create an express application. Express is a node JS Web application framework, which is very powerful, can create various Web applications and HTTP tools for users, and use the express framework to build a fully functional website.

 

Advantages of Express framework:

Middleware can be used to respond to HTTP requests, routing tables can be defined to execute different HTTP requests, and parameters can be passed to the template to dynamically render html pages.

To install the Express framework from the command line:

cnpm install express --save

The Express framework is installed on the node_modules directory, and then the following modules need to be installed together:

Body parser is node JS middleware can handle JSON, raw, text and URL encoded data. Cookie parser is a middleware for parsing cookies, and then through req Cookies can get the cookies passed and turn them into objects.

multer is node JS middleware, which is used to process the form data of enctype = "multipart / form data".

cnpm install body-parser --save
cnpm install cookie-parse --save
cnpm install multer --save

Let's take a look at the version number of the express framework:

cnpm list express

Create the first Express framework instance

Purpose: to output: "hello", name: express_demo.js file

// Introducing node module
const express = require('express');

// Create an express program
const app = express();

// Add HTTP route
app.get('/', function(request, response){
 // Output response message
 response.send('hello express');
});

// Start HTTP server
app.listen(8080, function(){
 console.log('express app');
});

Project execution:

node express_demo.js

Then you can use http://127.0.0.1:8080

The express framework uses the request object and response object to process the data of the request and response:

app.get('/', function(req,res){
})

 

The request object is an HTTP request

req.app

For callback, call back the external file of the function, using req App access instance of express

req.baseUrl

Gets the URL path of the current installation

req.body/req.cookies

To get "request subject"

req.hostname/req.ip

Get host name and ip address

req.originalUrl

Get original request URL

req.params

Get parameters of route

req.path

Get request path

req.protocol

Get protocol type

req.query

Get query parameters of URL

req.route

Get the current matching express route

req.subdomains

Get subdomain name

req.accepts()

Check the document type that can accept the request

req.get()

Gets the specified HTTP request header

req.is()

Determine the Mime type of the content type of the request header

 

The response object is an HTTP response

res.app

For callback, call back the external file of the function, and use res.app to access the instance of express

res.append()

Append the specified HTTP request header

res.set()

Reset the previously set request header after res.append()

res.clearCookie()

Clear cookies

res.download()

Transfer files in the specified path

res.get()

Returns the specified HTTP request header

res.json()

Send json response

res.jsonp transfer jsonp response

res.location() only sets the location HTTP request header of the response, and does not set the status code or close response

res.redirect() sets the location HTTP request header of the response and sets the status code 302

res.send() sends HTTP response

res.status() sets the HTTP status code

res.type() sets the MIME type of content type

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express routing

express route is composed of URI, HTTP request and several handles.

// Introducing node module
const express = require('express');

// Create an express program
const app = express();

// Add http route
app.get('/',function(request,response) {
 // Output response message
 response.send('hello dashucoding');
});

app.get('/users', function(req,res) {
 // req , res
 res.send('user');
});

// Start HTTP server
app.listen(8080, function(){
 console.lo('express app');
});

A GET request is a representation of a specified resource and is only used to obtain data

POST is used to submit the body to the specified resource

HEAD requests the same response as GET, but there is no response body

PUT is used to request the payload to replace all current representations of the target resource

DELETE deletes the specified resource

CONNECT establishes a tunnel for the server identified by the target resource

OPTIONS describes the communication OPTIONS of the target resource

PATCH is used to apply partial modifications to resources

app.get('/about',function(req,res){
res.send('about');
});

app.get('/ab?cd',function(req,res){
res.send('ab?cd');
}

app.get('/ab(cd)?e',function(req,res){
res.send('ab(cd)?e');
});

Route handle, which provides multiple callback functions for request processing, and the next('route ') method

let d1 = function(req,res,next){
 console.log('1');
 next();
};

let d2 = function(req,res,next){
 console.log('2');
 next();
});

let d3 = function(req,res,next){
 console.log('3');
 next();
 });
 
 app.get('/', [d1,d2]);

Next is used to execute the next callback function, and next('route ') is used to execute the next same route.

// Introducing node module
const express = require('express');
// Create an express program
const app = express();
// Add http route
app.get('/', function(request, response){
// Output response message
response.send('hello');
});
app.get('/users', function(req,res){
res.send('user');
});

// dynamic
app.get('/users/id', function(req,res){
let id = req.params.id;
// Return response
res.send('id='+id);
});

// Start HTTP server
app.listen(8080,function(){
console.log('expresss app');
});

const express = require('express');
const app = express();
app.get('/', function(request, response){
response.send('hello');
});
app.get('/users',function(req,res){
res.send('users');
});
app.param('id',(req,res,next)=>{
 console.log('hello');
 if(req.params.id==='1'){
 next();
 }else{
 res.sendStatus(404);
 }
 });
 
 app.get('/users/:id',(req,res)=>{
 res.send('hello');
 });
 
 // Start server
 app.listen(8080,function(){
  console.log('express');
 });

pug view template

Command line download:

npm install pug

pug.compile() compiles the pug code into a JavaScript function.

app.js

const express = require('express');

const app = express();

// Configure view template
app.set('view engine', 'pug');
app.set('views', './views');

// Add HTTP route
app.get('/', function(request, response){
response.render('index.pug');
// Output the response message, load and parse the index Pug file
});

app.get('/users',function(req,res){
res.render('users.pug',{
title:'user',
users:[
{id:1,name:'Zhang San',age:18}
]
});
});
// Start HTTP server
app.listen(8080,function(){
console.log('express');
});

users.pug:

doctype html
html
head
meta(charset="utf-8")
title #{title}
body
#app
 for user in users
 div
 p id=#{user.id}
 p name=#{user.name}
 p age=#{user.age}

pug.render()Template function:

const pug = require('pug');

console.log(pug.renderFile('template.pug',{
name:'dada'
});

Execute pug Renderfile() function will automatically store the compiled function in the internal cache

Tags: Framework

Posted by cesarcesar on Wed, 11 May 2022 01:48:02 +0300