Unsure how to use? about coinselect HOT 3 CLOSED

let feeRate = 100 // aka 100 satoshis per byte
let { inputs, outputs, fee } = coinselect([
  {
     txId: txId,
     vout: 1,
     value: txIdVal
  }
], [{
  address: this.state.add, // your desired output?
  value: amount
}], feeRate)

if (!inputs) throw new Error('No valid Transaction exists')

outputs.forEach((x) => {
  if (x.address) return
  x.address = this.state.address // the change address, if required
})

let txb = new bitcoin.TransactionBuilder(testnet)
inputs.forEach(x => txb.addInput(x.txId, x.vout))
outputs.forEach(x => txb.addOutput(x.address, x.value))
inputs.forEach((x, i) => txb.sign(i, keyPair))

txb.build().toHex()