Answers for "node get date at last moment of day"

moment js add day

var new_date = moment(startdate, "DD-MM-YYYY").add(5, 'days');

moment month start date and end date

const startOfMonth = moment().clone().startOf('month').format('YYYY-MM-DD hh:mm');
const endOfMonth   = moment().clone().endOf('month').format('YYYY-MM-DD hh:mm');