What are some examples of iterators in JavaScript?

What are some examples of iterators in JavaScript?

In JavaScript, iterators are objects that allow you to traverse through a collection, like arrays or strings. A common example is the Array.prototype.entries() method, which returns an iterator for the array's key/value pairs.

Can you show me how to use the for...of loop with an iterator?

Sure! You can use the for...of loop to iterate over the values of an iterable object. For example:

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

This will log 1, 2, and 3 to the console.

What about custom iterators? How can I create one?

You can create a custom iterator by defining an object with a next() method. Here's a simple example:

const myIterator = {
    current: 0,
    last: 5,
    next() {
        if (this.current < this.last) {
            return { value: this.current++, done: false };
        } else {
            return { done: true };
        }
    }
};

const iterator = myIterator;
console.log(iterator.next()); // { value: 0, done: false }
console.log(iterator.next()); // { value: 1, done: false }

Are there built-in iterators for strings?

Yes, strings in JavaScript are iterable by default. You can use the for...of loop to iterate over each character in a string. For example:

const str = 'hello';
for (const char of str) {
    console.log(char);
}

This will log each character of the string 'hello'.