~~~ const koa = require('koa'); const app = new koa(); var cors = require('koa2-cors'); var MongoClient = require('mongodb').MongoClient; const assert = require('assert'); app.use(cors({ origin: function (ctx) { //访问主域名下的test地址不允许跨域 if (ctx.url === '/test') { return false; } return '*'; }, exposeHeaders: ['WWW-Authenticate', 'Server-Authorization'], maxAge: 5, credentials: true, allowMethods: ['GET', 'POST', 'DELETE'], allowHeaders: ['Content-Type', 'Authorization', 'Accept'], })); var data = null; const url = 'mongodb://localhost:27017'; const dbName = 'smile-db'; MongoClient.connect(url, { useNewUrlParser: true }, function (err,client) { assert.equal(null, err); var movies = client.db(dbName).collection('movies'); movies.find({}).toArray(function(err,result){ if(err) throw err; //将数据返回给前台 app.use(async ctx => { ctx.body = result }) client.close() }) }); app.listen(8080) ~~~