Check if date is in the past without submitting form

Question

I have this code that I want to check if a date is in the past. I want to check it as soon as the date is entered, before form submission.

Answer 1

All you need to do is convert the string produced by the into a Date using the Date constructor new Date("2014-06-12")

 function checkDate() {
   var selectedText = document.getElementById('datepicker').value;
   var selectedDate = new Date(selectedText);
   var now = new Date();
   if (selectedDate < now) {
    alert("Date must be in the future");
   }
 }