CORS Policy blocking when accessing Adobe Rest APIs : Cloud Manager API Adobe IO Project

[Rite18]

i am getting error while accessing API for cloud Manager -  Adobe IO cloud Manager project has been setup in Adobe IO console works fine using Postman and getting expected response on the API call.

When i tried to replicate same in JS Code/Fetch call, getting below error 

has been blocked by CORS policy: Request header field access-control-allow-methods is not allowed by Access-Control-Allow-Headers in preflight response.

[Harwinder-singh · Accepted solution]

@Rite18 

Have you setup the Cross origin resource sharing (CORS) policy?

You basically need to add your custom domain from where you are trying to initiate this request as an allowed origin in the CORS policy.

Check  the below and see if these articles help: 

• https://experienceleague.adobe.com/docs/experience-manager-learn/foundation/security/develop-for-cro...
• https://experienceleague.adobe.com/docs/experience-manager-learn/foundation/security/understand-cros...
• https://github.com/AdobeDocs/adobeio-runtime/blob/master/guides/creating_rest_apis.md#enable-cors-on...
•  https://stackoverflow.com/questions/55869945/blocked-by-cors-policy-request-header-field-authorizati...

[EstebanBustamante]

You need to ensure:

• CORS is set up correctly as mentioned by @Harwinder-singh.

• Pay special attention to allowing the HTTP OPTIONS method, which is the type of method used for preflight operations.

• Make sure the dispatcher allows CORS headers and does not block the OPTIONS method.