How to use the @ethersproject/strings.nameprep function in @ethersproject/strings

function isValidName(name) {
    try {
        var comps = name.split(".");
        for (var i = 0; i < comps.length; i++) {
            if (strings_1.nameprep(comps[i]).length === 0) {
                throw new Error("empty");
            }
        }
        return true;
    }
    catch (error) { }
    return false;
}
exports.isValidName = isValidName;

export function isValidName(name) {
    try {
        const comps = name.split(".");
        for (let i = 0; i < comps.length; i++) {
            if (nameprep(comps[i]).length === 0) {
                throw new Error("empty");
            }
        }
        return true;
    }
    catch (error) { }
    return false;
}
export function namehash(name) {

export function isValidName(name: string): boolean {
    try {
        const comps = name.split(".");
        for (let i = 0; i < comps.length; i++) {
            if (nameprep(comps[i]).length === 0) {
                throw new Error("empty")
            }
        }
        return true;
    } catch (error) { }
    return false;
}

function namehash(name) {
    if (typeof (name) !== "string") {
        logger.throwArgumentError("invalid address - " + String(name), "name", name);
    }
    var result = Zeros;
    while (name.length) {
        var partition = name.match(Partition);
        var label = strings_1.toUtf8Bytes(strings_1.nameprep(partition[3]));
        result = keccak256_1.keccak256(bytes_1.concat([result, keccak256_1.keccak256(label)]));
        name = partition[2] || "";
    }
    return bytes_1.hexlify(result);
}
exports.namehash = namehash;

export function namehash(name) {
    if (typeof (name) !== "string") {
        logger.throwArgumentError("invalid address - " + String(name), "name", name);
    }
    let result = Zeros;
    while (name.length) {
        const partition = name.match(Partition);
        const label = toUtf8Bytes(nameprep(partition[3]));
        result = keccak256(concat([result, keccak256(label)]));
        name = partition[2] || "";
    }
    return hexlify(result);
}
export function id(text) {

export function namehash(name: string): string {
    if (typeof(name) !== "string") {
        logger.throwArgumentError("invalid address - " + String(name), "name", name);
    }

    let result: string | Uint8Array = Zeros;
    while (name.length) {
        const partition = name.match(Partition);
        const label = toUtf8Bytes(nameprep(partition[3]));
        result = keccak256(concat([result, keccak256(label)]));

        name = partition[2] || "";
    }

    return hexlify(result);
}