getErrorMessage.ts

// Helper function to determine error message.
const getErrorMessage = (error: Error | ErrorEvent | PromiseRejectionEvent): string => {
    // Set later.
    let message = '';

    // Message string?
    if (typeof (error as Error)?.message === 'string') {
        message = (error as Error)?.message;

        // Reason string?
    } else if (typeof (error as PromiseRejectionEvent)?.reason === 'string') {
        message = (error as PromiseRejectionEvent)?.reason;

        // Reason message string?
    } else if (typeof (error as PromiseRejectionEvent)?.reason?.message === 'string') {
        message = (error as PromiseRejectionEvent)?.reason?.message;
    }

    // Expose string.
    return message;
};

// Export.
export { getErrorMessage };