<!-- BEGIN COPY / PASTE -->
        class CustomError extends Error {
            constructor(message) {
                super(message);
                this.name = "CustomError";
            }
        }

        try {
            throw new CustomError("This is a custom error message.");
        } catch (error) {
            console.error(error.name + ": " + error.message);
        }
        <!-- END COPY / PASTE -->