Polkadot JS playground - Watch rewards on Controller account and print various diagnostics

rewards_watch.js

// Run your polkadot node 
// Copy and paste this snippet to https://polkadot.js.org/apps/#/js 
// update myStash with ID of the Stash account you'd like to watch
// You may leave this example running and it'll print updated balances of your RewardDestination.

const stash1 = '5GbphVim5aSCKVwPtruCKHfy4zmTMEUsm13hXcHn7n3y4geM';

const myStash = stash1;

//retrive AccountID the stash is bonded to, if any
const controllerAccID = await bondedTo(myStash);

if( controllerAccID === "" ){
  console.log('Account : ' + myStash,' is not bonded to a Controller!');
  return;
}

console.log('Your Stash account: ' + util.stringShorten(myStash,6), ' :');
console.log('... is bonded to Controller: ' + util.stringShorten(controllerAccID,6) );
await printStakeInfo(controllerAccID);
console.log('Rewards for the stake will be paid to: ');

//retrieve accountID that'll receive rewards at the end of an Era
const payee = await api.query.staking.payee(myStash);
//staking.payee() returns Enum
let payeeType = payee.toString();
let rewardsDestAccID = myStash;
switch(payeeType){
  case 'Controller':   
      rewardsDestAccID = controllerAccID;
      break;
  case 'Stash':
      payeeType = 'Stash, and the stake will not be increased';
      break;
  case 'Staked':
      payeeType = 'Stash, and the stake will be increased with each reward';
      break;
  default:
    console.error('Unknown payee destination returned: ' + payee.toString());
    return;
}
console.log('... ' + payeeType);
const isValidating = await isValidator(controllerAccID);
if(isValidating){
    await watchBalanceOf(rewardsDestAccID);
} else {
    console.log('Controller :',' associated with Stash: ',);
    console.log('... is not an active Validator');
    console.log('Session key for Controller is :');
    const sessionKey = await api.query.session.nextKeyFor(controllerAccID);
    console.log('... ' + (sessionKey.isSome ? sessionKey.value : "not set!"));
}

// --- helper functions ------------

async function watchBalanceOf(accountID){

  // Retrieve the initial balance.
  const startingBalance = await api.query.balances.freeBalance(accountID);
  
  console.log('Started monitoring at: ' + (new Date()).toString() );
  console.log('Account : ' + util.stringShorten(accountID,6),' had initial balance balance of: ' + util.formatBalance(startingBalance));
  
  let prevBalance = startingBalance;
  
  // Subscribe and listen to balance changes
  api.query.balances.freeBalance(accountID, (balance) => {
  
      // Calculate the delta
      const change = balance.sub(prevBalance);
      if(change != 0){
        console.log('Updated at: ' + (new Date()).toString() );
        console.log('new balance is: ' + util.formatBalance(balance),' delta is: ' + util.formatBalance(change));
        prevBalance = balance;
      } 
  });
  
}
// checks to see if accountID is currently an active Validator
async function isValidator(accountID){
  const validators = await api.query.session.validators();
  let accFound = false;
  for (let acc of validators) {
    if( acc.eq(accountID)){
      accFound = true;
      break;
    }
  }
  return accFound;
}
// print some info on stake, assumes that a bonded controller ID is provided
async function printStakeInfo(controllerID){
    const stLedgerOpt = await api.query.staking.ledger(controllerID);
    if(stLedgerOpt.isSome){
      const ledger = stLedgerOpt.value;
      const stashBalance = await api.query.balances.freeBalance(ledger.stash);
      console.log('... has total balance of: ' + util.formatBalance(stashBalance));
      console.log('... of which currently at stake are: ' + util.formatBalance(ledger.total));
    }
}
//checks whether accoundID is bonded to a Controller
async function bondedTo(accountID){
  let controller = await api.query.staking.bonded(accountID);
  //convert from Option & AccountId
  return controller.isSome ? controller.value.toString() : "";
}