【One by one系列】一步步学习node.js的web框架Koa

Koa快速入门

新建项目

mkdir koa-quick-start

cd koa-quick-start

npm init -yes

可以看到koa-quick-start下面有package.json

{
  "name": "koa-quick-start",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo "Error: no test specified" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
  }

下载koa包

npm install koa

再看package.json

{
  "name": "koa-quick-start",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo "Error: no test specified" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "koa": "^2.11.0"
  }
}

没错，多了koa的依赖

并且还多了node_modules文件夹

Hello Koa

新建文件index.js

键入如下代码

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

app.use(async (ctx, next) => {
    await next()
    ctx.response.type = 'text/html'
    ctx.response.body = '<h1>Hello World</h1>'
});

console.log("koa start,listen 3000...");
app.listen(3000);

运行起来

node index.js

koa start,listen 3000...