get_week_number_of_Month.js

function getWeekOfMonth(date) {
    let adjustedDate = date.getDate()+date.getDay();
    let prefixes = ['0', '1', '2', '3', '4', '5'];
    return (parseInt(prefixes[0 | adjustedDate / 7])+1);
}

function getDateOfWeek(w, y) {
    var d = (1 + (w - 1) * 7); // 1st of January + 7 days for each week

    return new Date(y, 0, d);
}

function getDateOfISOWeek(w, y) {
    var simple = new Date(y, 0, 1 + (w - 1) * 7);
    var dow = simple.getDay();
    var ISOweekStart = simple;
    if (dow <= 4)
        ISOweekStart.setDate(simple.getDate() - simple.getDay() + 1);
    else
        ISOweekStart.setDate(simple.getDate() + 8 - simple.getDay());
    return ISOweekStart;
}