Sign Solana transaction from back end and send to chain

signTransaction.ts

import { Transaction, Connection, clusterApiUrl } from "@solana/web3.js";

const connection = new Connection(clusterApiUrl("devnet"));

// Get the wallet object from your wallet provider
const wallet = useWallet()

export async function signTransaction(transaction) {
  // 1. Get transaction form back end and construct buffer form it.
  const serializedTransaction = Buffer.from(transaction, "base64");
  const txt = Transaction.from(serializedTransaction);

  // 2. Sign the transaction
  const signedTransaction = await wallet.signTransaction(txt);

  // 3. Send transaction to blockchain
  const signature = await connection.sendRawTransaction(
    signedTransaction.serialize()
  );

  // 4. Await confirmation on the blockchain
  const result = await connection.confirmTransaction(signature);
  return { result, signature };
}