Cross-origin request in javascript-js

I have added the header (& quot; Access-Control-Allow-Origin: * & quot;); To the backend ;);, but why does the {code...} still appear when the front-end uses js requests ...} I have added header("Access-Control-Allow-Origin:*");But why does the front-end still appear when using js requests?

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://nichijou.org/x. (Reason: CORS header 'Access-Control-Allow-Origin' missing). Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://nichijou.org/x. (Reason: CORS request failed).

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I have addedheader("Access-Control-Allow-Origin:*");But why does the front-end still appear when using js requests?

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://nichijou.org/x. (Reason: CORS header 'Access-Control-Allow-Origin' missing). Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://nichijou.org/x. (Reason: CORS request failed).

1. Many browsers do not support this function.*To setAccess-Control-Allow-OriginThe normal practice isheader("Access-Control-Allow-Origin:".$_SERVER['HTTP_HOST']);

2. If you want to transmit cookiesAccess-Control-Allow-Credentials: trueThis header is used. Specific can see the document: https://developer.mozilla.org/en-US/docs/Web/HTTP/Server-Side_Access_Control

Which browsers are listed in the version number?