前端ajax跨域问题及基于node的跨域解决方案No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.

 

百度了半天都说是跨域问题，

解决办法：

设置请求头解决跨域

res.setHeader('Access-Control-Allow-Origin', '*'); //设置请求头解决跨域

app.get('/song_sheet',function(req,res){
    connection.query('select * from song_sheet',function(error,results,fields){
        res.setHeader('Access-Control-Allow-Origin', '*'); //设置请求头解决跨域
        res.send(results)
        // console.log(results)
        console.log(error)
    })
})

解决问题

 参考自：https://blog.csdn.net/weixin_45014444/article/details/96734242