BTC OP_RETURN

btc_opreturn.js

// // package.json
// {
//   "dependencies": {
//     "bitcoincashjs": "^0.1.10",
//     "bitcore-explorers": "^1.0.1",
//   }
// }
const fs = require('fs')
const bitcoin = require('bitcoincashjs') // npm i bitcoincashjs --save
// ( see https://bitcore.io/api/lib for docs )

const Transaction = bitcoin.Transaction

// Private key part
// ---

// // generate and save private key
// const pvt = new bitcoin.PrivateKey()
// console.log(pvt.toString('hex'))

// load private key from a file
const privateKeyString = fs.readFileSync('./private-key.txt').toString().trim()

// load private key from local string
// const privateKeyString = "your-private-key-as-string"

const privateKey = new bitcoin.PrivateKey(privateKeyString)
const address = privateKey.toAddress().toString()
console.log("loaded private key")
console.log("address:", address)


// UTXOs part
// ---

var Insight = require('bitcore-explorers').Insight;
var insight = new Insight("https://blockdozer.com");

const getUTXOs = (address) => {
  return new Promise((resolve, reject) => {
    insight.getUnspentUtxos(address, (err, data) => {
      if (err) { reject(err); return }
      resolve(data)
    })
  })
}

const pushTx = (rawTx) => {
  return new Promise((resolve, reject) => {
    insight.broadcast(rawTx, (err, txId) => {
      if (err) { reject(err); return }
      resolve(txId)
    })
  })
}


;(async () => {

  // get utxos
  let utxos = await getUTXOs(address)
  console.log("UTXOs selection:")
  console.log(utxos)
  console.log("------------")

  utxos = [utxos[0]]
  console.log(utxos)

  // // create transaction
  let tx = new Transaction()
    .from(utxos)
    .to(address, 10000) // minimum amount
    .change(address)   // send and refund on the same address
    .fee(10000)

  // add OP_RETURN script
  tx = tx.addData(' { "appliedblockchain": "rulez", "lorem": "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut...." }')

  // signing with local private key
  tx = tx.sign(privateKey)

  const rawTx = tx.serialize()

  const txId = await pushTx(rawTx)
  console.log("TX:", txId)

  console.log(`https://blockchair.com/bitcoin-cash/transaction/${txId}`)

})()