Mastering Immutable.js

The ultimate lazy pattern

This brings us to our ultimate lazy pattern. On their own, filter() and map() are powerful tools. You can add reduce() to the sequence as well, despite the fact that it isn't lazy. However, this doesn't stop the map() and filter() calls from executing lazily:

const capitalize = s =>  `${s.charAt(0).toUpperCase()}${s.slice(1)}`;const pick = (m, ...props) =>  props.map(p => m.get(p));const myList = List.of(  Map.of('first', 'joe', 'last', 'brown', 'age', 45),  Map.of('first', 'john', 'last', 'smith', 'age', 32),  Map.of('first', 'mary', 'last', 'wise', 'age', 56));console.log('myList', myList.toJS());// -> myList [ { first: 'joe', last: 'brown', age: 45 },// -> { first: 'john', last: 'smith', age: 32 },// -> { first: 'mary', ...