Hari 14: Iterators & Generators

Iterator Protocol

// Objek iterable mengimplementasikan [Symbol.iterator]
const range = {
    from: 1,
    to: 5,
    [Symbol.iterator]() {
        let current = this.from;
        const last = this.to;
        return {
            next() {
                return current <= last
                    ? { value: current++, done: false }
                    : { value: undefined, done: true };
            }
        };
    }
};

for (const n of range) process.stdout.write(n + " ");
// 1 2 3 4 5
console.log([...range]); // [1, 2, 3, 4, 5]

Generator Function

function* fibonacci() {
    let [a, b] = [0, 1];
    while (true) {
        yield a;
        [a, b] = [b, a + b];
    }
}

const fib = fibonacci();
const sepuluhFib = Array.from({ length: 10 }, () => fib.next().value);
console.log(sepuluhFib); // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

// Generator sebagai range
function* range(start, end, step = 1) {
    for (let i = start; i <= end; i += step) yield i;
}
console.log([...range(0, 10, 2)]); // [0, 2, 4, 6, 8, 10]