addBlockhash.ts

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

export async function addBlockhash(
  connection: Connection,
  transaction: Transaction
): Promise<void> {
  for (let i = 0; i < 5; i++) {
    try {
      transaction.recentBlockhash = await getBlockhash(connection);
      break;
    } catch (e) {
      // retry;
    }
  }

  if (!transaction.recentBlockhash)
    throw new Error('Unable to get blockhash, please retry');
}

async function getBlockhash(connection: Connection): Promise<string> {
  try {
    const {blockhash} = await connection.getLatestBlockhash();
    return blockhash;
  } catch (e) {
    const {blockhash} = await connection.getRecentBlockhash();
    return blockhash;
  }
}