// IsAjaxRequest checks and returns whether current request is an AJAX request. func (r *Request) IsAjaxRequest() bool {return strings.EqualFold(r.Header.Get("X-Requested-With"), "XMLHttpRequest") } 根据X-Requested-With的值为XMLHttpRequest

跨域的简单原理：一般浏览器会阻止js请求异端服务器（A服务器请求B服务器）。js连接却除外 如：<script type="text/jscript" src="http://www.yourtour.cc/ajax_test.js"></script> 还有iframe、css、script 都