How to use the sodium-javascript.crypto_sign_BYTES function in sodium-javascript

ed.sign = function (hash, keyPair) {
    const sig = Buffer.alloc(sodium.crypto_sign_BYTES);
    sodium.crypto_sign_detached(sig, hash, keyPair.privateKey);
    return sig;
};

Block.prototype.sign = function (block, keyPair) {
    const blockHash = this.getHash(block);
    const sig = Buffer.alloc(sodium.crypto_sign_BYTES);

    sodium.crypto_sign_detached(sig, blockHash, keyPair.privateKey);
    return sig.toString('hex');
};

Transaction.prototype.sign = (keyPair, trs) => {
    const sig = Buffer.alloc(sodium.crypto_sign_BYTES);

    sodium.crypto_sign_detached(sig, self.getHash(trs), keyPair.privateKey);
    return sig.toString('hex');
};

private sign(block, keyPair): Response {
        const blockHash = this.getHash(block);
        if (!blockHash.success) {
            return new Response({ errors: [...blockHash.errors, 'sign'] });
        }

        const sig = Buffer.alloc(sodium.crypto_sign_BYTES);
        sodium.crypto_sign_detached(sig, blockHash.data, keyPair.privateKey);
        return new Response({ data: sig.toString('hex') });
    }

Transaction.prototype.sign = function (keyPair, trs) {
    const sig = Buffer.alloc(sodium.crypto_sign_BYTES);

    sodium.crypto_sign_detached(sig, this.getHash(trs), keyPair.privateKey);
    return sig.toString('hex');
};