polygon_blocktime.js

// https://rxjs.dev/api
const { from, timer } = require('rxjs');
const { last, map, catchError, switchMap } = require('rxjs/operators');
// https://danfo.jsdata.org/
const dfd = require('danfojs-node');

let latestBlocktime = 2.2;

function getBlocktime() {
  return from(dfd.readCSV('https://polygonscan.com/chart/blocktime?output=csv')).pipe(
    catchError((error) => {
      console.error(error);
      return from(Promise.resolve(null));
    }),
    map((df) => {
      const value = parseFloat(df['Value'].tail(1).values[0]);
      if (isNaN(value)) {
        throw new Error('Latest value is NaN');
      }
      latestBlocktime = value;
      return latestBlocktime;
    }),
    last()
  );
}

function main() {
  // update every 5mins
  timer(0, 5 * 60 * 1000)
    .pipe(switchMap(() => getBlocktime()))
    .subscribe({
      next: (latestFloatValue) => {
        console.log('return val:', latestFloatValue);
        console.log('global val:', latestBlocktime);
      },
      error: (error) => {
        console.error(error);
      },
      complete: () => {
        console.log('Done!');
      },
    });
}

main();

// Export latestBlocktime as a global variable
global.latestBlocktime = () => latestBlocktime;