How to Add a Memo to a Transaction

import {
  airdropFactory,
  appendTransactionMessageInstructions,
  createSolanaRpc,
  createSolanaRpcSubscriptions,
  createTransactionMessage,
  generateKeyPairSigner,
  getSignatureFromTransaction,
  lamports,
  pipe,
  sendAndConfirmTransactionFactory,
  setTransactionMessageFeePayerSigner,
  setTransactionMessageLifetimeUsingBlockhash,
  signTransactionMessageWithSigners
} from "@solana/kit";
import { getAddMemoInstruction } from "@solana-program/memo";

const rpc = createSolanaRpc("http://localhost:8899");
const rpcSubscriptions = createSolanaRpcSubscriptions("ws://localhost:8900");

const sender = await generateKeyPairSigner();
const LAMPORTS_PER_SOL = 1_000_000_000n;
await airdropFactory({ rpc, rpcSubscriptions })({
  recipientAddress: sender.address,
  lamports: lamports(LAMPORTS_PER_SOL), // 1 SOL
  commitment: "confirmed"
});

const memoInstruction = getAddMemoInstruction({
  memo: "Hello, world!"
});

const { value: latestBlockhash } = await rpc.getLatestBlockhash().send();
const transactionMessage = pipe(
  createTransactionMessage({ version: 0 }),
  (tx) => setTransactionMessageFeePayerSigner(sender, tx),
  (tx) => setTransactionMessageLifetimeUsingBlockhash(latestBlockhash, tx),
  (tx) => appendTransactionMessageInstructions([memoInstruction], tx)
);

const signedTransaction =
  await signTransactionMessageWithSigners(transactionMessage);
await sendAndConfirmTransactionFactory({ rpc, rpcSubscriptions })(
  signedTransaction,
  { commitment: "confirmed" }
);
const transactionSignature = getSignatureFromTransaction(signedTransaction);
console.log("Transaction Signature:", transactionSignature);