1- 安装模块

yarn add koa koa-router koa2-cors
cnpm i nodemon -g

models/top250.js

//models/top250.js
const mongoose = require("mongoose");
/* 1.连接本地数据库 */
mongoose.connect( 'mongodb://127.0.0.1:27017/movies', {useNewUrlParser: true});
/* 2.在本地定义一个Schema和远程的数据库的字段映射 */
var Top250Schema = new mongoose.Schema({
    name:String,
    rating:Number
});
/* 3.创建数据模型,和数据库中的表映射,获取表   */
/* Top250Model  是我们获取的top250那张表 */
var Top250Model = mongoose.model("top250",Top250Schema,"top250")
module.exports = Top250Model;

index.js

//index.js
const koa = require("koa");
const router = require("koa-router")();
const Top250Model = require("./models/top250");
const cors = require("koa2-cors");
const app = new koa();
/* top250路由去读取数据库中的数据 */
router.get("/top250",async ctx=>{
    var data = await Top250Model.find({})
    ctx.body = {
        data,
        code:200
    }
})
app.use(cors());
app.use(router.routes());
app.listen(8080)