nodejs学习

创建一个Nodejs项目

npm init 生成 package.json

hongyun@ubuntu:/opt/vue/test$ npm init
This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.

See `npm help init` for definitive documentation on these fields
and exactly what they do.

Use `npm install <pkg>` afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
package name: (test) 
version: (1.0.0) 
description: test 
entry point: (index.js) 
test command: 
git repository: 
keywords: 
author: 
license: (ISC) 
About to write to /opt/vue/test/package.json:

{
  "name": "test",
  "version": "1.0.0",
  "description": "test ",
  "main": "index.js",
  "scripts": {
    "test": "echo "Error: no test specified" && exit 1"
  },
  "author": "",
  "license": "ISC"
}


Is this OK? (yes) 


   ╭─────────────────────────────────────────────────────────────────╮
   │                                                                 │
   │      New patch version of npm available! 6.14.8 → 6.14.11       │
   │   Changelog: https://github.com/npm/cli/releases/tag/v6.14.11   │
   │                Run npm install -g npm to update!                │
   │                                                                 │
   ╰─────────────────────────────────────────────────────────────────╯

hongyun@ubuntu:/opt/vue/test$ 

"main": "index.js" 这个项目的入口是index.js

安装一个模块

npm install express@3.21.2

hongyun@ubuntu:/opt/vue/test$ ll
total 44
drwxrwxr-x  3 hongyun hongyun  4096 2月   1 09:28 ./
drwxrwxr-x  3 hongyun hongyun  4096 2月   1 09:15 ../
drwxrwxr-x 80 hongyun hongyun  4096 2月   1 09:28 node_modules/
-rw-rw-r--  1 hongyun hongyun   255 2月   1 09:28 package.json
-rw-rw-r--  1 hongyun hongyun 25441 2月   1 09:28 package-lock.json

hongyun@ubuntu:/opt/vue/test$ cat node_modules/express/index.js 

module.exports = require('./lib/express');