本文通过设置Access-Control-Allow-Origin(CORS)来实现跨域。
例如:客户端的域名是client.runoob.com,而请求的域名是server.runoob.com。
如果直接使用ajax访问,会有以下错误:
XMLHttpRequest cannot load http://server.runoob.com/server.php. No 'Access-Control-Allow-Origin' header is present on the requested resource.Origin 'http://client.runoob.com' is therefore not allowed access.