Error while creating Graph API Access token

Hi guys,

I am trying to create an access token for calling Graph API through browser.  When I call 'https://login.microsoftonline.com/XXXX-XXXX-XXX-XXX-XXX/oauth2/token' api using AJAX, I receive below error.

Access to XMLHttpRequest at 'https://login.microsoftonline.com/XXXX-XXXX-XXX-XXX-XXX/oauth2/token' from origin 'https://cevalogisticsoffice365.sharepoint.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

Please can you provide me why this error is occurring and what is the solution for this. 

Regards