ExpressJs 是控制台记录两次

Question

我不明白为什么我只创建一个服务器并在浏览器中加载一次时我的代码记录消息两次。

输入-

const express = require('express');

const app = express();

app.use((req, res, next) => {
    console.log('Hello middleware')
    next(); // Allows the request to continue to the next middleware in line
});

app.use((req, res, next) => {
    console.log('Hello middleware v2')
    res.send('<h1>Hello Express!</h1>');
});

app.listen(3000);

输出 -

[nodemon] restarting due to changes...
[nodemon] starting `node app.js`
Hello middleware
Hello middleware v2
Hello middleware
Hello middleware v2

package.json -

{
  "name": "nodeproject1",
  "version": "1.0.0",
  "description": "node tutorial",
  "main": "app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon app.js"
  },
  "author": "Arkapratim Sarkar",
  "license": "ISC",
  "devDependencies": {
    "nodemon": "^2.0.6"
  },
  "dependencies": {
    "express": "^4.17.1"
  }
}

Answer 1

如果您通过浏览器执行请求，不仅会针对相应的请求路径（例如/）发送请求，还会针对/favicon.ico发送请求（详细说明here). 由于发出了两个请求，您会看到每个中间件的日志消息两次。

ExpressJs 是控制台记录两次

ExpressJs is console logging two times

node.js

express

nodemon