// ES6 version separating out the generation of the fibonacci sequence

function * fibGen() {
    yield 1;
    yield 1;

    const lastTwo = [1, 1];

    while (true) {
        const next = lastTwo[0] + lastTwo[1];
        lastTwo.push(next);
        lastTwo.shift();

        yield next;
    }
}


function sumOddFib(n) {
    let total = 0;

    for (const fib of fibGen()) {
        if (fib >= n) break;
        total += fib % 2 ? fib : 0;
    }

    return total;
}


// ES5 version

function sumOddFibV2(n) {
    if (n === 1) return 1;
    if (n === 2) return 2;

    var total = 2;
    var lastTwo = [1, 1];

    while (true) {
        var next = lastTwo[0] + lastTwo[1];
        lastTwo.push(next);
        lastTwo.shift();

        if (next >= n) break;

        total += next % 2 ? next : 0;
    }

    return total;
}