/* eslint-disable header/header */
/* eslint-disable @typescript-eslint/require-await */
/* eslint-disable @typescript-eslint/unbound-method */

// Import the API
const { ApiPromise } = require('@polkadot/api');

async function main () {
  // Create a new instance of the api
  const api = await ApiPromise.create();

  // Subscribe to chain updates and log the current block number on update.
  const unsubscribe = await api.rpc.chain.subscribeNewHeads((header) => {
    console.log(`Chain is at block: #${header.number}`);
  });

  // In this example we're calling the unsubscribe() function that is being
  // returned by the api call function after 20s.
  setTimeout(() => {
    unsubscribe();
    console.log('Unsubscribed');
  }, 20000);
}

main().catch(console.error);