get transaction hash before send

getTxHash.js

  let txIdCalculated = null
  const getTxHash = async () => {
    const txIdFromChain = await sdk.decode(
      await sdk.send(
        await sdk.resolve(
          await sdk.build([
            sdk.transaction`transaction(msg: String) { prepare(acct: AuthAccount) {} execute { log(msg) } }`,
            sdk.args([sdk.arg("Hello, Flow!", t.String)]),
            sdk.payer(fcl.currentUser().authorization),
            sdk.proposer(fcl.currentUser().authorization),
            sdk.authorizations([fcl.currentUser().authorization]),
            sdk.preSendCheck(async voucher => {
              txIdCalculated = sdk.voucherToTxId(voucher)
            }),
          ])
        ),
        {node: "https://access-testnet.onflow.org"}
      )
    )
    console.log("TX ID", txIdFromChain)
    console.log("Pre calculated TxID", txIdCalculated)
    invariant(txIdCalculated === txIdFromChain, "Uh oh, didn't work")
  }