Let's modify our example slightly, building on this lazy mapping pattern. It's common to filter collections before mapping them so that they only include relevant values:

myList
  .toSeq()
  .filter(v => v.get('age') > 35)
  .map(v => v.update('first', capitalize))
  .map(v => v.update('last', capitalize))
  .map(v => [v.get('first'), v.get('last')].join(' '))
  .forEach(v => console.log('name', v));
  // -> name Joe Brown
  // -> name Mary Wise

In this case, we only want capitalized names where age is over 35. Once a filter match is found, it flows through each of the map() calls.