BITBOX to spend P2SH output w/ custom script generated w/ https://gist.github.com/cgcardona/f72dcd476b9860bfaeba431f4a576eb8

spend-p2sh-output.js

let BITBOXCli = require("bitbox-sdk/lib/bitbox-sdk").default;
let BITBOX = new BITBOXCli();

let main = async () => {
  let mnemonic = "put your mnemonic here";

  // root seed buffer
  let rootSeed = BITBOX.Mnemonic.toSeed(mnemonic);

  // master HDNode
  let masterHDNode = BITBOX.HDNode.fromSeed(rootSeed, "bitcoincash");

  // HDNode of BIP44 account
  let account = BITBOX.HDNode.derivePath(masterHDNode, "m/44'/145'/0'");

  // derive HDNode
  let node = BITBOX.HDNode.derivePath(account, "0/0");

  // cashAddress
  let cashAddress = BITBOX.HDNode.toCashAddress(node);

  // custom script from create-p2sh-output.js
  const script = BITBOX.Script.encode([
    Buffer.from("BOX", "ascii"),
    BITBOX.Script.opcodes.OP_CAT,
    Buffer.from("BITBOX", "ascii"),
    BITBOX.Script.opcodes.OP_EQUAL
  ]);

  // hash160 script buffer
  const p2sh_hash160 = BITBOX.Crypto.hash160(script);

  // encode hash160 as P2SH output
  const scriptPubKey = BITBOX.Script.scriptHash.output.encode(p2sh_hash160);

  // get p2sh address from output script
  const p2shAddress = BITBOX.Address.fromOutputScript(scriptPubKey);

  // fetch uxto from rest.bitcoin
  let result = await BITBOX.Address.utxo(p2shAddress);

  // create instance of TransactionBuilder
  const transactionBuilder = new BITBOX.TransactionBuilder();

  // original amount of satoshis in vout
  const originalAmount = result[0].satoshis;

  // index of vout
  const vout = result[0].vout;

  // txid of vout
  const txid = result[0].txid;

  // add input
  transactionBuilder.addInput(txid, vout);

  // calculate tx size for fee of 1 sat/b
  let byteCount = BITBOX.BitcoinCash.getByteCount({ P2PKH: 2 }, { P2PKH: 1 });
  let sendAmount = originalAmount - byteCount;

  // add output
  transactionBuilder.addOutput(cashAddress, sendAmount);

  // encode locking script
  let encodedScript = BITBOX.Script.encode(script);

  // HDNode to keypair
  let keyPair = BITBOX.HDNode.toKeyPair(node);

  // create unlocking script
  let script2 = [Buffer.from("BIT", "ascii")];

  // concat scripts together
  let children = script2.concat(script);

  // encode scripts
  let encodedScript2 = BITBOX.Script.encode(children);

  // set input script
  transactionBuilder.addInputScript(vout, encodedScript2);

  // build to hex
  const hex = transactionBuilder.build().toHex();

  // POST to BCH network
  let success = await BITBOX.RawTransactions.sendRawTransaction(hex);
  console.log("success: ", success);
};

main();