Ist die Woche ein grader oder ungrader Turnus

turnus.js

// Kalenderwoche, in denen schule ist.
const schoolWeeks = [ 2, 6, 9, 12, 17, 20, 23, 26 ];

const weekNumber = (d = new Date()) =>
{
    let startDate = new Date(d.getFullYear(), 0, 1);
    // EDIT: 19.03.2023
    let days = Math.floor((d - startDate) / (7 * 24 * 60 * 60 * 1000));
    return Math.ceil(days / 7);
};

const getCycle = () =>
{
    const wn = schoolWeeks.indexOf(weekNumber());
    return wn < 0
        ? 'Arbeitswoche'
        : ( wn % 2
            ? 'odd week (u.T.)'
            : 'regular week (g.T.)');
};

// Display the calculated result       
console.log(getCycle());