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This article mainly explains "how to use the Express framework in Node.js". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Now let the editor take you to learn how to use the Express framework in Node.js.

Many languages have frameworks that can help us develop and maintain projects more quickly, such as JS has popular frameworks such as Vue, React, Angular, and Node.js is no exception, it also has frameworks that can help us develop Node.js projects.

At present, the popular Node.js frameworks are Express, Koa and Egg.js, no matter which Node.js framework is based on middleware, and the execution mode of middleware needs to be based on the onion model.

Onion model

An abstract explanation is that if you pass through the onion central point, you must first penetrate the onion epidermis layer by layer into the central point, and then layer by layer from the central point out of the epidermis. There is a characteristic here: how many layers of epidermis are worn when entering and how many layers of epidermis must be worn out when you go out. First into the epidermis, then out of the epidermis, this structure is in line with the stack structure of the principle of first in and then out.

In the Node.js framework, the skin of onions can be defined as middleware:

The process of entering the center point from outside to inside is a keyword next ()

From the inside to the outside, after the execution of each middleware, enter the next layer of middleware, all the way to the last layer.

Let's take a brief look at some Express frameworks!

Express

Express is a framework for HTTP services in Node.js, and the best way to understand a framework is

To understand its key functions.

Deduce what the problem it wants to solve is.

To understand its key functions, we can go to Express's website to check its Features. These core functions are for us to write HTTP services more conveniently and succinctly, thus greatly reducing our development burden and allowing us to get started quickly.

Some Features:

Routing: treat the corresponding routes separately as modules

The simplification of the request/response attribute allows us to use the corresponding attribute directly without having to transform it.

Request:pathname, query, etc.

Response:send (), json (), jsonp (), etc.

Middleware (next ())

Better organize process codes

Asynchronism will break Express's onion model.

Express revamped the game of rock scissors paper

Now by using the Express framework to modify the rock scissors paper game, game.js game module and index.html page code has not changed, you can go to github above clone.

For index.js Express transformation, it is necessary to install express:npm I express with npm first.

Const fs = require ('fs'); const express = require (' express'); const game = require ('. / game'); let playerWon = 0; / / the number of wins const app = express () / / routing function, which treats the corresponding routing function separately as a module, and then can also be placed in other files / / the route of / favicon.ico path is set through app.get / / .get represents that the request method is get, so post, delete and so on can be used here. This capability is suitable for creating rest service app.get ('/ favicon.ico', function (request, response) {/ / a status sentence can replace writeHead; end (); / response.writeHead (200); / / response.end (); response.status (200); return }) / / Open the page index.htmlapp.get ('/', function (request, response) {/ / fs.createReadStream (_ _ dirname +'/ index.html') .pipe (response) / / the send API will determine the type of the value you passed in. If the text is processed as text/html / / Buffer, it will be processed as download. The html file needs to be added with `utf- 8`response.send (fs.readFileSync (_ _ dirname +'/ index.html', 'utf-8')}) / / next (). There is no problem in synchronous state, but once there is async. The onion model breaks app.get ('/ game', function (request, response, next) {if (playerWon > = 3) {response.status (500) Response.send ('I won't play anymore!') ; return;} / / execute the subsequent middleware next () through next; / / when the subsequent middleware is executed, it will be executed to this location if (response.playerWon) {playerWon++ }}, / / get the player's operation function (request, response, next) {/ / Express has done some processing on request, you can directly get the query parameter / / const query = querystring.parse (parsedUrl.query); / / const playerAction = query.action; const query = request.query; const playerAction = query.action; response.playerAction = playerAction; / / execute the subsequent middleware next () through next }, function (request, response) {/ / Mount some parameters let playerAction = response.playerAction; / / execute game logic const gameRes = game (playerAction) via response; / / return the header / / response.writeHead first; response.status (200) / / return different instructions according to different game results if (gameRes = = 0) {/ / response.end ('tie!') ; response.send ('tie!') ;} else if (gameRes = = 1) {response.send ('you win!') ; / / player victory count + 1 / / playerWon++; response.playerWon = true;} else {response.send ('you lost!') App.listen (3000); at this point, I believe you have a deeper understanding of "how to use the Express framework in Node.js". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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