prependTransactionInstructions if you need to prepend multiple instructions to a transaction message.
import { address } from '@solana/addresses';
import { prependTransactionMessageInstruction } from '@solana/transaction-messages';
const memoTransaction = prependTransactionMessageInstruction(
{
data: new TextEncoder().encode('Hello world!'),
programAddress: address('MemoSq4gqABAXKb96qnH8TysNcWxMyWCqXgDLGmfcHr'),
},
tx,
);
Given an instruction, this method will return a new transaction message with that instruction having been added to the beginning of the list of existing instructions.