What are JavaScript iterators and how do they work?

What are JavaScript iterators and how do they work?

JavaScript iterators are objects that allow you to traverse through a collection, like arrays or strings, one element at a time.

Can you give me an example of a custom iterator?

Sure! Here's a simple custom iterator for an array:

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

You can use it like this:

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

What is the difference between an iterator and an iterable?

An iterable is an object that can be iterated over, like arrays or strings, and it must implement the Symbol.iterator method. An iterator, on the other hand, is the object that actually performs the iteration, providing the next() method to access the elements.

How do I use the for...of loop with iterators?

You can use the for...of loop to iterate over any iterable. For example:

const myArray = [1, 2, 3];
for (const value of myArray) {
    console.log(value);
}

This will log each value in the array.