get.first.day.of.week.js

function getFirstDayOfWeek(date) {
    if (!date) {
        date = new Date();
    }
    var firstDay = new Date(date - (date.getDay() - 1) * 86400000);
    return firstDay;
}
function getLastDayOfWeek(date) {
    if (!date) {
        date = new Date();
    }
    var firstDay = new Date(date - (date.getDay() - 1) * 86400000);
    var lastDay = new Date((firstDay / 1000 + 6 * 86400) * 1000);
    return lastDay;
}
function getFirstDayOfMonth(date) {
    if (!date) {
        date = new Date();
    }
    var firstDay = new Date(date.getYear(), date.getMonth(), 1);
    return firstDay;
}
function getLastDayOfMonth(date) {
    if (!date) {
        date = new Date();
    }
    var nextFirstDayOfMonth = new Date(date.getYear(), date.getMonth() + 1, 1);
    var lastDay = new Date(nextFirstDayOfMonth - 86400000);
    return lastDay;
}