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

上传图片 跨域请求 出现异常

delete jQuery.ajaxSettings.headers['sessionId']

jQuery.ajaxSettings.headers['sessionId'] = Cookies.get("sessionId");

//上传图片功能
function uploadImg(file) {
var fd = new FormData();
fd.append('uploadFile', file);

//删除请求头中的sessionid
delete jQuery.ajaxSettings.headers['sessionId']

$.ajax({
url:uploadUrl,
type: "post",
// Form数据
dataType:'json',
data: fd,
cache: false,
contentType: false,
processData: false,
beforeSend:function(xhr){
//删除请求头中的sessionid  这里不一定可以，在本项目中，就不行
//  delete jQuery.ajaxSettings.headers['sessionId']
},
success: function (data) {
//                jQuery.ajaxSettings.headers['sessionId'] = Cookies.get("sessionId");
linkImage = data.visitPath;

//上传成功，展示在页面上  展示 linlUrl
$("#linkImage").attr("src",linkImage);
}

});

//将数据设置回去

a27b
jQuery.ajaxSettings.headers['sessionId'] = Cookies.get("sessionId");

}