koa接口跨域报错

Question

用koa+mongodb写了几个接口,用ajax请求时总是跨域报错,koa中用了cors也不行,谷歌了好多还是没有解决问题const cors = require('koa2-cors');var MongoClient = require("mongodb").MongoClient;var DB_URL = "mongodb://localhost:27017/test";// app.use(cors());app.use(cors({    origin: function (ctx) {            return "*"; // 允许来自所有域名请求    },    exposeHeaders: ['WWW-Authenticate', 'Server-Authorization'],    maxAge: 5,    credentials: true,    allowMethods: ['GET', 'POST', 'DELETE'],    allowHeaders: ['Content-Type', 'Authorization', 'Accept'],}))//省略封装的函数代码app.use(router['routes']());router.get('/',findFn)router.get('/add',insertFn)app.listen(3000);让我的localhost:1234/index.html页面里请求localhost:3000的接口就会报如上图的错误(Failed to load localhost:3000: Cross origin requests are only supported for protocol schemes: http, data, chrome, chrome-extension, https.)望大家指点一二,谢谢

Answer 1

你的错误不是跨域的错误，看起来是你直接本地打开发的请求，起个服务打开试试

Answer 2

从response上看不是后端代码的问题，贴一下前端代码，错误信息说only supported for protocol schemes:http, data, chrome, chrome-extension, https，怀疑是你scheme写错。