What is an iterator in JavaScript?

Can you explain what an iterator is in JavaScript?

Sure! An iterator is an object that allows you to traverse through a collection, like an array, one element at a time.

How does an iterator work in practice?

An iterator works by implementing two methods: next() which returns the next value and done which indicates if the iteration is complete.

Can you give me an example of a custom iterator?

Absolutely! Here's a simple example:

function createIterator(array) {
    let index = 0;
    return {
        next: function() {
            if (index < array.length) {
                return { value: array[index++], done: false };
            } else {
                return { done: true };
            }
        }
    };
}

const myIterator = createIterator([1, 2, 3]);
console.log(myIterator.next()); // { value: 1, done: false }
console.log(myIterator.next()); // { value: 2, done: false }
console.log(myIterator.next()); // { value: 3, done: false }
console.log(myIterator.next()); // { done: true }

What are some built-in iterators in JavaScript?

Some built-in iterators in JavaScript include the Array iterator, Map iterator, and Set iterator, which allow you to loop through their elements.