import { ServiceError, ServiceStatus, serviceCall } from 'grpc-js-helper';

// ..

try {
    const result = await serviceCall(serviceClient.method1());
} catch (error) {
    if (error instanceof ServiceError) {
        switch (error.code) {
            case ServiceStatus.UNAVAILABLE:
                // do something
                break;
        }
    } else {
        // should be unreachable
    }
}