Javascript Iterator is an object or pattern that allows us to traverse over a list or collection. Iterators define the sequences and implement the iterator protocol that returns an object by using a next() method that contains the value and is done. The value contains the next value of the iterator sequence and the done is the boolean value true or false if the last value of the sequence has been consumed then it’s true else false.

We can check if any entity is by default iterable or not We can check its prototype and can see if it is having a method Symbol(Symbol.iterator) or not.

In Array.prototype you will find Symbol(Symbol.iterator): ƒ values() method. The array is by default iterable. Also, String, Map & Set are built-in iterables because their prototype objects all have a Symbol.iterator() method.