How to use Psbt on bitcoinjs-lib?

I am trying to create a raw transaction for sending to the blockchain. In doing so, I want to do this in a browser.

Where can I get nonWitnessUtxo?

All the information that I have outlined here, I found in the tests. Am I doing the right thing?

const bitcoin = require('bitcoinjs-lib')
const testnet = bitcoin.networks.testnet
const keyPair = bitcoin.ECPair.makeRandom({ network: testnet })
const publicKey = keyPair.publicKey
const { address } = bitcoin.payments.p2pkh({
  pubkey: publicKey,
  network: testnet
})
const privateKey = keyPair.toWIF()
const psbt = new bitcoin.Psbt({ network: testnet })
const txid = '226a14d30cfd411b14bf20b7ffd211f7f206699690c54d456cc1bef70c2de5a6'
const key = bitcoin.ECPair.fromWIF(privateKey, testnet)
psbt.addInput({
  hash: txid,
  index: 0,
  nonWitnessUtxo: Buffer.from('Where can i get this?', 'hex')
})
psbt.addOutput({
  script: Buffer.from('mmpAPZSvhJs1NGw8UaJXEJ9vRByAxProUL', 'hex')
  value: 10000
})
psbt.signInput(0, key)
psbt.validateSignaturesOfInput(0)
psbt.finalizeAllInputs()
psbt.extractTransaction().toHex()

I would be grateful for any help!

This answer is for those looking for a way to create a transaction in the browser, but could not deal with the bitcoinjs-lib

I use bitcore-lib - https://www.npmjs.com/package/bitcore-lib

const bitcore = require('bitcore-lib')

const firstPrivateKey = new bitcore.PrivateKey()
const secondPrivateKey = new bitcore.PrivateKey() 

const wif = firstPrivateKey.toString()
const toAddress = secondPrivateKey.toAddress().toString()
const satoshiAmount = 10000

const privateKey = bitcore.PrivateKey.fromWIF(wif)
const sourceAddress = privateKey.toAddress(bitcore.Networks.testnet)
const targetAddress = bitcore.Address.fromString(toAddress)
const utxos = [
  {
    address: 'mywRqUpbENhbu5VsYDwiMTJouVK9g2ZEJQ',
    txid: '761693565e82ca176532c52a37fb38cd9f1eb0172a00562b394e60ede0b7df8a',
    vout: 1,
    scriptPubKey: '76a914ca133ceac705b723b91263aa163ea8a45954e49a88ac',
    amount: 0.0001,
    satoshis: 10000,
    height: 1578273,
    confirmations: 338
  }
]
const transaction = new bitcore.Transaction()

transaction.from(utxos)
transaction.to(targetAddress, Number(satoshiAmount))
transaction.change(sourceAddress)
transaction.sign(privateKey)

const serializedTX = tx.serialize()

Then you need send this serializedTX as raw transaction to bitcoin network.

P.S. This example does not work because there is an invalid is presented utxos. Get your utxos using API, such as https://bitpay.com/api/addr/${sourceAddress}/utxo and then everything will work.