How can I use Symbol.iterator in my classes?

How can I use Symbol.iterator in my classes?

You can implement the Symbol.iterator method in your class to make it iterable. Here's a simple example.

Can you show me a code example?

Sure! Here's a class that uses Symbol.iterator:

class MyCollection {
    constructor() {
        this.items = [];
    }
    add(item) {
        this.items.push(item);
    }
    [Symbol.iterator]() {
        let index = 0;
        return {
            next: () => {
                if (index < this.items.length) {
                    return { value: this.items[index++], done: false };
                } else {
                    return { done: true };
                }
            }
        };
    }
}

This allows you to use a for...of loop on instances of MyCollection.

What if I want to iterate in reverse?

You can modify the Symbol.iterator method to start from the end of the array. Here's how:

[Symbol.iterator]() {
    let index = this.items.length - 1;
    return {
        next: () => {
            if (index >= 0) {
                return { value: this.items[index--], done: false };
            } else {
                return { done: true };
            }
        }
    };
}

That's great! Can I also use other iterable methods?

Absolutely! You can implement other iterable methods like entries() or keys() to customize your iteration further.