Sets & Iterators

The last step to working with Sets is looping over them.

If you remember back to our discussion on the new iterable and _iterator protocols _in ES6, then you’ll recall that Sets are built-in iterables. This means two things in terms of looping:

1. You can use the Set’s default iterator to step through each item in a Set, one by one.
2. You can use the new for...of loop to loop through each item in a Set.

Using the SetIterator

Because the.values()method returns a new iterator object (calledSetIterator), you can store that iterator object in a variable and loop through each item in the Set using.next().

const iterator = months.values();
iterator.next();

Object {value: 'January', done: false}

And if you run.next()again?

iterator.next();

Object {value: 'February', done: false}

And so on untildoneequalstruewhich marks the end of the Set.

Video

Using afor...ofLoop

An easier method to loop through the items in a Set is thefor...ofloop.

const colors = new Set(['red', 'orange', 'yellow', 'green', 'blue', 'violet', 'brown', 'black']);
for (const color of colors) {
  console.log(color);
}

red
orange
yellow
green
blue
violet
brown
black