JavaScript - Set.keys() Method

The Set.keys() method in JavaScript returns an iterator object containing the values of the elements in a Set object, in insertion order.

This method is an alias for the JavaScript values() method.

Syntax

Following is the syntax of JavaScript Set.keys() method −

keys()

Parameters

This method does not accept any parameters.

Return value

This method returns an iterator object containing the values of the elements in the set, in insertion order.

Examples

Example 1

In the following example, we are iterating through the element of the Set object using the keys() method and printing them with a for...of loop from the result of the keys() method.

<html>
<body>
   <script>
      const set = new Set();
      set.add('apple');
      set.add('banana');
      set.add('cherry');
      
      const iterator = set.keys();
      for (const value of iterator) {
         document.write(value, "<br>");
      }
   </script>
</body>
</html>

The above program returns a new set iterator object "iterator" that contains the values of this Set in insertion order.

Example 2

In this example, we're using the keys() method to create an iterator for the values in the Set. Then, we manually retrieve each value using the next() method on the iterator.

<html>
<body>
   <script>
      const set = new Set();
      set.add('a');
      set.add('b');
      set.add('c');
      
      const iterator = set.keys();
      
      document.write(iterator.next().value, "<br>");
      document.write(iterator.next().value, "<br>");
      document.write(iterator.next().value);
   </script>
</body>
</html>

As we can see in the output, it returned each value present in the set.

Example 3

In the following example, we are using the spread operator (...) to convert the iterator returned by the values() method into an array containing all the values of the set.

<html>
<body>
   <script>
      const mySet = new Set(["apple", "banana", "orange"]);
      const valuesArray = [...mySet.values()];
      document.write(valuesArray);
   </script>
</body>
</html>

If we execute the above program, it returns an array containing each value from the set.