create and broadcast op_return data to bitcoin blockchain by using polar and bitcoinjs.

gistfile1.js

var bitcoin = require('bitcoinjs-lib');
const Client = require('bitcoin-core');
const client = new Client({ network: 'regtest',port: 18443, username: 'polaruser', password: 'polarpass', version: '0.21.1' });

async function sendopreturn() {
    try {
        const unspentutxos = await client.command('listunspent');
        // console.log("unspentutxos: ", unspentutxos);
    
        // get a random UTXO
        const randomutxo = unspentutxos[Math.floor(Math.random()*unspentutxos.length)];
        console.log(`randomutxo: `, JSON.stringify(randomutxo));
    
        // get privkey for the utxo
        const wif = await client.command(`dumpprivkey`, randomutxo.address);
        // console.log("privkey for the utxo: ", wif);

        // use bitcoinjs-lib psbt to get raw op_return tx
        const alice = bitcoin.ECPair.fromWIF(wif, bitcoin.networks.regtest);
        const inputData1 = {
            hash: randomutxo.txid,
            index: randomutxo.vout,
            witnessUtxo: {script: Buffer.from(randomutxo.scriptPubKey, 'hex'), value: parseInt(randomutxo.amount*100000000)}
          };
        // this is opreturn data - can be anything under 80 bytes
        const data = Buffer.from('03729d8e7a3bfcffc65b4f97df0bdbb128339a7110a1c1b33d8462d1355fc7ba', 'hex');
        const embed = bitcoin.payments.embed({ data: [data] });
        const psbt = new bitcoin.Psbt({ network: bitcoin.networks.regtest })
          .addInput(inputData1)
          .addOutput({
            script: embed.output,
            value: 0,
          })
          .addOutput({
            address: 'bcrt1q7xp6jcgmnuvvaqzr9sdg7yjdqfftswjdqz9897',
            value: 500000,
          })
          .addOutput({
            address: randomutxo.address,
            value: parseInt(randomutxo.amount*100000000)-501000,
          })
          .signInput(0, alice);
    
        psbt.finalizeAllInputs();

        const txHex = psbt.extractTransaction().toHex();
        console.log(`txHex ${txHex}`);

        await client.command(`sendrawtransaction`, txHex);
        console.log("raw tx sent: ", txHex);
    } catch (error) {
        console.log("error: ", error);
    }
}
sendopreturn();