Входы и выходы из / в HTML и JS

function calc() {
  // get corresponding value from input
  var inDate = document.getElementById('inDate').value;
  var outDate = document.getElementById('outDate').value;

  // allow calculations if both input fields have values, otherwise error can occur while calculating date
  if (inDate && outDate) {


    // convert to date format
    var date1 = new Date(inDate);
    var date2 = new Date(outDate);


    // code for checking date1 > date 2 if you want 
    //calculations 
    var timeDiff = Math.abs(date2.getTime() - date1.getTime());
    var diffDays = Math.ceil(timeDiff / (1000 * 3600 * 24));

    //for Displaying in html
    document.getElementById('stay').innerHTML = diffDays;

  }

}

// adding event so that when we change any one of the field, the functuion will calculate the daydiff and display in the html page
document.getElementById('outDate').addEventListener("change", calc);
document.getElementById('inDate').addEventListener("change", calc);

<form>
  <p>Select your Check-in date please</p>
  <input id = "inDate" type = "date">

  <p>Select your Check-out date please</p>
  <input id = "outDate" type = "date">

  <span>You are staying </span><span id = "stay"></span> <span> days with us.</span>

</form>