What is the difference between iterable objects and iterators in TypeScript?

What is the difference between iterable objects and iterators in TypeScript?

In TypeScript, iterable objects are those that implement the iterable protocol, meaning they have a method that returns an iterator. An iterator, on the other hand, is an object that implements the iterator protocol, which includes a next() method that returns the next value in the sequence.

Can you give me an example of an iterable object?

Sure! An example of an iterable object is an array. In TypeScript, you can use the for...of loop to iterate over an array, which utilizes its iterable protocol.

What about a custom iterable object?

You can create a custom iterable object by implementing the Symbol.iterator method. This method should return an iterator object that defines the next() method.

Can you show me a code example of that?

Absolutely! Here's a simple example:

class MyIterable {
    private items: number[];

    constructor(items: number[]) {
        this.items = items;
    }

    [Symbol.iterator]() {
        let index = 0;
        const items = this.items;
        return {
            next(): IteratorResult<number> {
                if (index < items.length) {
                    return { value: items[index++], done: false };
                } else {
                    return { value: undefined, done: true };
                }
            }
        };
    }
}

const iterable = new MyIterable([1, 2, 3]);
for (const item of iterable) {
    console.log(item);
}

This will log 1, 2, and 3.