Generators and Iterators

Expert-Level Explanation

Generators and iterators in JavaScript are advanced concepts used to handle sequences of data. An iterator is an object that allows us to traverse a collection, one element at a time. A generator is a special type of function that works as a factory for iterators. It can pause midway and resume where it stopped.

Creative Explanation

Think of a generator as a novel writing machine. It writes one page (which yields a value) each time you ask (call next()). You can read the page (consume the value) and then ask for the next page when you're ready, pausing as needed. An iterator is like a bookmark, keeping track of your place in a book (collection).

Practical Explanation with Code

function* numberGenerator() {
    yield 1;
    yield 2;
    yield 3;
}

const gen = numberGenerator(); // "gen" is the Iterator
console.log(gen.next().value); // 1
console.log(gen.next().value); // 2
console.log(gen.next().value); // 3

Real-world Example

A generator is like a music playlist. You play a song (yield a value), pause it, do something else, then resume the playlist (call next()) from where you left off. The iterator (music player) keeps track of which song is up next.