先来一个hello,world

目录结构

新建package.json

mkdir koa2scd koa2snpm init

新建index.js

const koa = require('koa');const app = new koa();app.listen(3000);console.log(`app start at localhost:3000`);

安装依赖，执行

cnpm install koa --savenode index.js

新建数据，返回hello,world

修改index.js

const koa = require('koa');const app = new koa();app.use(async(ctx, next) => {    ctx.response.body = "
hello,world
"})app.listen(3000);console.log(`app start at localhost:3000`);

重新运行

node index.js