Checks if the air is polluted given a threshold and a number of samples.

Check Air Quality

const checkAir = function (samples, threshold) {
  //tallies the dirty samples
  let pollution = 0;
  for (let sample in samples){
    if (samples[sample] === 'dirty'){
      pollution++;
    }
  }
  //checks if the total dirty samples exceed the threshold
  if ((pollution /= samples.length) >= threshold){
    return 'Polluted';
  } else{
    return 'Clean';
  }
};