listingAlertBot.js

const axios = require('axios');

const apiURL = "https://api.helius.xyz/v0/addresses";
const address = "9MynErYQ5Qi6obp4YwwdoDmXkZ1hYVtPUqYmJJ3rZ9Kn"; // DeGods
const resource = "nft-events";
const options = `api-key=<your-api-key-here>&type=NFT_LISTING`;
let mostRecentTxn = "";
const listingThreshold = 200; // SOL
const LAMPORTS_PER_SOL = 1000000000;

const listingAlertBot = async () => {
  while(true) {
    const url = `${apiURL}/${address}/${resource}?${options}&until=${mostRecentTxn}`;
    const { data } = await axios.get(url);
    if (!data.length) { continue; }
    const alertTxns = data.find(x => x.amount < listingThreshold * LAMPORTS_PER_SOL);
    console.log("Txns: ", alertTxns);
    mostRecentTxn = data[0].signature;
  } 
}
listingAlertBot();