javascript validate form by separate by comma

Use variable with javascript inner HTML  

var str = document.getElementById("elementID").value

var res = str.split(" ")

res.length

Script javascript 

<script type="text/javascript">

function valicontact() {

  var x = document.getElementById("inputFirstname").value;

  var res = x.split(",")

  var y = document.getElementById("signum").value;

  var ress = y.split(",")

  var z = document.getElementById("Contactno").value;

  var resss = z.split(",")

  var n = res.length

  var s = ress.length

  var c = resss.length

  if (s == c && s == n){

  Sbutton.style.display = "block";

  document.getElementById("errormessage").innerHTML = ""

  } else {

  document.getElementById("errormessage").innerHTML = "Number of Name,Signum and Contact should be same <br> name =" + n + "<br> Signum = " + s + "<br> Contact =" +c;

  Sbutton.style.display = "none";

  }

  

}

</script>