generators.js

function simpleIterator() {
    const iterator = {
        next() {
            return {
                value: "Hello, I'm an iterator",
                done: true,
            };
        },
    };

    const result = iterator.next();
    console.log(result.value);
    console.log(result.done);
}

function helloWorld() {
    const words = ["Hello", "World"];
    let index = 0;

    const iterator = {
        next() {
            return {
                value: words[index++],
                done: index === words.length + 1,
            };
        },
    };

    let result = iterator.next();
    console.log(result.value, result.done);

    result = iterator.next();
    console.log(result.value, result.done);

    result = iterator.next();
    console.log(result.value, result.done);
}

function helloWorldIterable() {
    const words = ["Hello", "World"];
    let index = 0;

    const iterator = {
        next() {
            return {
                value: words[index++],
                done: index === words.length + 1,
            };
        },
    };

    const iterable = {
        [Symbol.iterator]() {
            return iterator;
        },
    };

    for (let word of iterable) {
        console.log(word);
    }
}

function iteratorAndIterable() {
    const iteratorAndIterable = {
        next() {
            // ...
        },
        [Symbol.iterator]() {
            return this;
        },
    };
}

function generatorExample() {
    function* generateHelloWorld(name) {
        yield "Hello";
        yield "World";
        yield name;
    }

    const generator = generateHelloWorld("Tomasz");

    for (let word of generator) {
        console.log(word);
    }
}

generatorExample();