javascript - html js upload keeps getting error in http request, please give me some advice

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

Access-Control-Allow-Origin:* has been set up on the server. What kind of problem might this be?

Please give me some advice on how to solve it

Reply content:

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

Access-Control-Allow-Origin:* has been set up on the server. What kind of problem might this be?

Please give me some advice on how to solve it

From here it is a cross-domain problem
header("Access-Control-Allow-Origin: source domain name");
header("Access-Control-Allow-Credentials:true");