Parse raw transaction to get output address?

[maxsummers]

Hello!

Is it possible to use this module in order to parse raw transaction data and get destination Bitcoin addresses from it?

I've managed to parse raw transaction from hex string:

const bitcoinJs = require('bitcoinjs-lib');

const rawTx = '010...000';

const tx = bitcoinJs.Transaction.fromHex(rawTx);

console.log(JSON.stringify(tx, null, 4));

But how do I get destinations addresses from it?

Thank you.

[maxsummers]

Well, looks like I've finally managed to extract address from script output.

Here's my implementation:

const _ = require('lodash');
const bitcoinJs = require('bitcoinjs-lib');
const Buffer = require('buffer').Buffer;

const rawTx = '010...000';

const tx = bitcoinJs.Transaction.fromHex(rawTx);

_.forEach(tx.outs, out => {
  if (bitcoinJs.script.isPubKeyHashOutput(out.script)) {
    const pubKey = Buffer.from(out.script, 3, 20);
    const address = bitcoinJs.address.fromOutputScript(pubKey);
    console.log(address);
  }
});

Is this a most optimal way to do this? Do you have any suggestions of how I can improve it?

Is it enough to only check for PubKeyHashOutput for general transactions? Or do I need to implement some other script types also?

---

The library is very well written, it was a pleasure reading it's source code. Great job!

Thanks.

[afk11]

Don't forget about script-hash outputs, they also have an address!

[dcousens]

let bitcoinjs = require('bitcoinjs-lib')

// ...
let tx = bitcoinjs.Transaction.fromHex('010...000')

tx.outs.forEach((out) => {
  let address
  try {
    address = bitcoinjs.address.fromOutputScript(out.script)
  } catch (e) {}

  if (address) console.log(address)
})

@afk11 to be honest, I do the above so often, I'd rather just have no error thrown and instead return null...

Maybe fromOutputScriptUnsafe

[dcousens]

It seems most people do this too, or they have some other assumption that means they can rely on it not throwing.
In any case, I think null would avoid the try/catch boiler plate.

https://github.com/xorq/easybtc/blob/46c8821cee303aed829160fd50eb2269e290a9d4/models/crypto.js#L432
https://github.com/darkwallet/darkwallet/blob/4c51dacacb8541305f1442ef7fa1628eb7c19a79/src/js/frontend/controllers/browser.js#L56
https://github.com/CoinSpace/cs-wallet/blob/ee49f55018dc2b275a799682c6343a474b69b51d/lib/wallet.js#L158
https://github.com/blocktrail/blocktrail-webwallet/blob/f87fb007c918c723d9de206e0c28238211f7a7a1/src/lib/blocktrail-sdk/lib/wallet.js#L298

The only question is whether we make a new method to avoid breaking people who upgrade without looking at the CHANGELOG.

[maxsummers]

Oh, thank you @dcousens . Is bitcoinjs.address.fromOutputScript(out.script) enough to parse all commonly used transaction types?

[dcousens]

@maxsummers it is enough to obtain an "address" from the 2 commonly used script types that have addresses: P2PKH, P2SH.
It does not support stealth addresses, or other complex ECDH protocols.

[maxsummers]

Thank you, this really helps.