node+koa項目初始化1

1. 創建項目文件夾island
2. 進入文件夾執行npm init 生成package.js文件
3. 執行npm i koa --save命令安裝koa
4. 在跟目錄下創建app.js入口文件

const Koa = require('koa')
const app = new Koa()

// next() 返回promise，前面添加await關鍵字後會返回求值結果
// async和await必須成對出現
// await 我們可以理解爲求值關鍵字 例如await 100*100 得到的是10000
// 爲了保證洋蔥模型，koa中間件中都加 async和await

// app.use 註冊中間件
app.use(async(ctx, next)=>{
  console.log(1)
  await next()
  console.log(2)
})
app.use((ctx, next)=>{
  console.log(3)
})

// 設置服務器端口
app.listen(3000)

5. 執行node app.js命令，並在瀏覽器中打開http://localhost:3000/
6. 安裝所有依賴

{
  "name": "island",
  "version": "1.0.0",
  "description": "node+koa搭建後臺api",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "[email protected]:carol02/island.git"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "axios": "^0.19.0",
    "basic-auth": "^2.0.1",
    "bcryptjs": "^2.4.3",
    "jsonwebtoken": "^8.5.1",
    "koa": "^2.7.0",
    "koa-bodyparser": "^4.2.1",
    "koa-static": "^5.0.0",
    "lodash": "^4.17.15",
    "mysql2": "^1.6.5",
    "npm-check": "^5.9.0",
    "require-directory": "^2.1.1",
    "sequelize": "^5.14.0",
    "validator": "^11.1.0"
  }
}