post请求(headers里有属性)报错：Request header field xxx is not allowed by Access-Control-Allow-Headers in preflight response

• post 请求，headers里有属性（xxx）。请求时报错：

XMLHttpRequest cannot load <url>. Request header field xxx is not allowed by Access-Control-Allow-Headers in preflight response.

解决：在后端的Access-Control-Allow-Headers里，添加该 field。