http请求头部信息的获取方法：

let req = new XMLHttpRequest();req.open(‘GET‘, document.location, false);req.send(null);console.log(req)let content=req.getResponseHeader(‘content-type‘)
console.log(content)

var headers = req.getAllResponseHeaders().toLowerCase();console.log(headers);

 参考链接：https://www.bbsmax.com/A/WpdK0OrzVQ/