Get date of start of week

startOfWeek.js

function startOfWeek (weekStart) {
  
  var today = new Date();
  var todayInWeek = today.getDay();
  var todayDate = today.getDate();
  var startOfWeekDate = (weekStart == "m") ? 
      todayDate - (todayInWeek - 1) : todayDate - todayInWeek;
  
  var startOfWeek = new Date();

  startOfWeek.setDate(startOfWeekDate);
  
  return startOfWeek;

}


console.log(startOfWeek("s"));