JS method to get the current day of the week from Monday to Sunday

function getWeekDay(dateString) {
    let dateStringReg = /^\d{4}[/-]\d{1,2}[/-]\d{1,2}$/;

    if (dateString.match(dateStringReg)) {
        let presentDate = new Date(dateString),
            today = presentDate.getDay() !== 0 ? presentDate.getDay() : 7;

        return Array.from(new Array(7), function(val, index) {
            return formatDate(new Date(presentDate.getTime() - (today - index-1) * 24 * 60 * 60 * 1000));
        });

    } else {
        throw new Error('dateString should be like "yyyy-mm-dd" or "yyyy/mm/dd"');
    }

    function formatDate(date) {
        return date.getFullYear() + '-' + (date.getMonth() + 1) + '-' + date.getDate();
    }
}

getWeekDay('2019-9-5')
//["2019-9-2", "2019-9-3", "2019-9-4", "2019-9-5", "2019-9-6", "2019-9-7", "2019-9-8"]