I am just learning this but found this information in the doco:
MSAL.js Angular readme:
protectedResourceMap : Mapping of resources to scopes {"https://graph.microsoft.com/v1.0/me", ["user.read", "mail.send"]}. Used internally by the MSAL for automatically attaching tokens in webApi calls. This is required only for CORS calls.
My understanding of the given example is:
export const protectedResourceMap:[string, string[]][]=[
['your api endpoint',['scope 1', 'scope 2', 'scope n']] // example
['https://buildtodoservice.azurewebsites.net/api/todolist',['api://a88bb933-319c-41b5-9f04-eff36d985612/access_as_user']], // api you host
['https://graph.microsoft.com/v1.0/me', ['user.read']] // ms graph api - uses short scope names with no uri prefix
];
So when calling the path 'your api endpoint' include the token associated with the scopes 'scope 1', 'scope 2', 'scope n'.