SharePoint on MS Graph: Authentication Provider

dlAuthenticationProvider.ts

export class DLAuthenticationProvider implements AuthenticationProvider {
    config: MsalConfig = {
        auth: {
            clientId: '',
            authority: '',
            clientSecret: '',
            graphendpoint: '',
        }
    };
    tokenrequest: any;
    cca: msal.ConfidentialClientApplication;

    constructor(config: MsalConfig) {
        this.config = config;
        this.tokenrequest = {
            scopes: [config.auth.graphendpoint + '.default'],
        };
        this.cca = new msal.ConfidentialClientApplication(this.config);
    }

    public async getAccessToken(): Promise<string> {
        return new Promise((ok, fail) => {
            this.cca.acquireTokenByClientCredential(this.tokenrequest)
                .then((response) => {
                    ok(response.accessToken);
                })
                .catch((error) => {
                    fail(error);
                })
        })
    }

}