koa2 实现跨域

koa2 设置允许跨域需要用到 koa2-cors 插件
npm 地址 https://www.npmjs.com/package/koa2-cors

server.js 中这样写

const Koa = require('koa');
const Router = require('koa-router');
const cors = require('koa2-cors');

let server = new Koa()
server.listen(3001)

// 解决跨域
server.use(cors({
    origin: function (ctx) {
        return '*'  // 允许来自所有域名请求
       // return 'http://localhost:8080'; / 这样就能只允许 http://localhost:8080 这个域名的请求了
    },
    exposeHeaders: ['WWW-Authenticate', 'Server-Authorization'],
    maxAge: 5,
    credentials: true,
    allowMethods: ['GET', 'POST', 'DELETE', 'OPTIONS', 'PUT'],
    allowHeaders: ['Content-Type', 'Authorization', 'Accept'],
}))

let router = new Router();


router.get('/test', async ctx => {
    ctx.body = {
        code: 200,
        data: '测试的啊',
        msg: ''
    }
})

前端 代码

this.$axios.get('http://172.16.186.50:3001/')
     .then((response) => {
         console.log(response)
     })
     .catch(function (error) {
         console.log(error);
     });

也没有跨域报错信息了