Convert input into string/var and use it in an alert

Question

I am using an input and want to covert it into a string/var to print it out in an alert after i click on a button.

I need the input of "Forename:" to add into the button "send" with "onlcick".

The alert is just a debuger. Instead of alert i want to use a function. Using onclick="printPDF(foreName+' '' ' + da + '.' + mo + '.' + ye + '_' + h + ':' + m + ':' + s + '.pdf');

function startTime() {
  var today = new Date();
  var da = today.getDate();
  var mo = today.getMonth() + 1;
  var ye = today.getFullYear();
  var h = today.getHours();
  var m = today.getMinutes();
  var s = today.getSeconds();
  m = checkTime(m);
  s = checkTime(s);
}

function checkTime(i) {
  if (i < 10) {
    i = "0" + i
  }; // add zero in front of numbers < 10
  return i;
}

<p>
  <label>Forename:</label>
  <input class="w3-input w3-white" id="some1" type="text" name="some1" value="asd" maxLength="200">
</p>

<button id="snbtn1" type="submit" class="w3-btn w3-green" onclick="alert(' ' + da + '.' + mo + '.' + ye + '_' + h + ':' + m + ':' + s + '.pdf');">send</button>

Answer 1

<script>
function startTime() {
      var today = new Date();
      var da = today.getDate();
      var mo = today.getMonth()+1;
      var ye = today.getFullYear();
      var h = today.getHours();
      var m = today.getMinutes();
      var s = today.getSeconds();
      m = checkTime(m);
      s = checkTime(s);
      var foreName = document.getElementById('some1').value;

      alert(foreName+' ' + da + '.' + mo + '.' + ye + '_' + h + ':' + m + ':' + s + '.pdf');
}

function checkTime(i) {
  if (i < 10) {i = "0" + i};  // add zero in front of numbers < 10
  return i;
}
</script>
<p>
    <label>Forename:</label>
    <input class="w3-input w3-white" id="some1" type="text" name="some1" value="asd" maxLength="200">
</p>

   <button id="snbtn1" type="submit" class="w3-btn w3-green"  onclick="startTime();">send</button>