CORS AJAX呼叫失败

Question

I have an AJAX call trying to execute the following CORS request to a Web Server (I am currently testing using only the latest version of Chrome):

var xhr = new XMLHttpRequest();
xhr.open("get", "http://www.web_server_url.com/query", true);
xhr.onload = function(){
};
xhr.send(null);

Meanwhile, I am still getting the following message:

XMLHttpRequest cannot load http://www.web_server_url.com/query. Origin http://localhost is not allowed by Access-Control-Allow-Origin.

Would someone know what I am missing?

Answer 1

The reason is exactly what it says in the error: The server at www.web_server_url.com is not allowing the localhost origin. It's up to the server to decide whether to allow the origin of the call. In this case, apparently it's not allowing it.

The way CORS works, the server replies to the request (or a "preflight" request) with headers either allowing or disallowing the origin on the basis of the information the browser sends it.