Ethers calculate transaction fee

EthersTxGasCalculations.js

import { ethers } from "ethers";

// Using this if cannot serialize bigint
BigInt.prototype.toJSON = function () {
  const int = Number.parseInt(this.toString());
  return int ?? this.toString();
};

// Define provider 
const provider = new ethers.JsonRpcProvider(RPC_URL)

// Define signer 
const signer = new ethers.Wallet(
private_key,
provider
);
 
 // Define Contract
 const myContract = new ethers.Contract(
  address,
  contractAbi,
  signer
);

// *Optional: Test tx if can pass. It returns true or error
const testTx =
  await myContract.oneMethod.staticCall(
    oneParameter,
    anotherParameter
  );

// Estimate Gas
const gasAmount =
  await myContract.oneMethod.estimateGas(
    oneParameter,
    anotherParameter
  );
// Get the current gas price
const gasPrice = (await provider.getFeeData()).gasPrice;
// Calculate the gas fee
const gasFeeInWei = (gasPrice as bigint) * gasAmount;
const gasFeeInETH = ethers.formatEther(gasFeeInWei);