参考页面：https://blog.csdn.net/idomyway/article/details/79572973
如果请求的是PHP页面：
header("Access-Control-Allow-Origin: *");
解决 js ajax跨域访问报“No 'Access-Control-Allow-Origin' header is present on the requested resource.”错误
原文：https://www.cnblogs.com/gavinyyb/p/10672982.html