USDT Transfer Gas Fee on Tron

USDTTronGas.js

const bs58 = require('bs58');
const axios = require("axios");

const triggerUrl = "https://api.trongrid.io/wallet/triggerconstantcontract";
const energyUnitUrl = "https://api.trongrid.io/wallet/getenergyprices";

// amount should not include decimals
// sender and receiver should be in base58
async function getFee(sender, receiver, amount) {
  const decimals = 10**6; //USDT decimals
  amount = Number(amount*decimals).toString(16);
  amount = Array(64-amount.length).fill(0).join("") + amount; // amount in ABI encoded hex
  
  // convert receiver to hex
  const receiverHex = Buffer.from(
    bs58.decode(receiver)
  )
    .toString('hex')
    .slice(0,42);
  
  const data = {
    owner_address: sender,
    contract_address: "TR7NHqjeKQxGTCi8q8ZY4pL8otSzgjLj6t", // USDT Address
    function_selector: "transfer(address,uint256)",
    parameter: `0000000000000000000000${receiverHex}${amount}`, // abi encoded parameters
    "call_value": 0,
    "visible": true
  }

  // get latest energy unit price in SUN (WEI equivalent)
  const energyUnitPriceHistory = (await axios.post(energyUnitUrl)).data.prices;
  const energyUnitPrice = energyUnitPriceHistory.split(":").pop();
  
  // get energy used for transaction
  const res = await axios.post(triggerUrl, data);
  const energyUsed = res.data.energy_used;
  
  // get total fee and convert to TRX :fee = energy used * energy unit price, 1000000 SUN = 1 TRX
  const fee = parseInt(energyUsed) * parseInt(energyUnitPrice) / 1000000

  return fee;
}

feePromise = getFee("TCTxqwRdh1uvzHPXFQMMZ3StJCBA7A5Ycg", "TNb3CCAfd4CmBojKpJVn9iuJ4j52NbWoZ1", 30);

feePromise.then(console.log);