preflight response 应该是异步的什么问题---后来发现不是，是axios参数格式问题，网上其他一些解答太误导人了

Request header field Content-Type is not allowed by Access-Control-Allow-Headers in preflight response.

用的axios做的请求，express后端返回，post请求时报这个错

设置Axios.post('/api-user/login/login', params, {headers: {'sign': sign}}); 后面的sign时报

　　Request header field sign is not allowed by Access-Control-Allow-Headers in preflight response.

原因？求解

----------------------------------------------------------

let params={name:'hhl',psd:'123456'};
let out=Axios.get('/login',{params:params});  //格式不这么写就报 in preflight response

let out2=Axios.post('/login/abort', qs.stringify(params) ); //post需要用qs来转化一下

axios没有配置什么，express配置跨域

app.all('*', function(req, res, next) {
　　res.header("Access-Control-Allow-Origin", "*");
　　res.header("Access-Control-Allow-Headers", "X-Requested-With");
　　res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");
　　res.header("X-Powered-By",' 3.2.1');
　　res.header("Content-Type", "application/json;charset=utf-8");
　　next();

}

其中主要是origin，好像

问题已解决