function calc()
{
  var kw = document.getElementById("keyword").value;
  kw = kw.toLowerCase();
  var kws = kw.split(" ");
  
  var txt = document.getElementById("text").value;
  var origtxt = txt;  
  
  txt = txt.replace(/[\.\?\!;:,]/g, "").toLowerCase();
  txt = txt.replace(/\s\s/g, " ");
  var woorden = txt.split(" ");
  var aantal = 0;
  
  for (var i = 0; i < woorden.length; i++)
  {
    for (var j = 0; j < kws.length; j++)
    {
      if (woorden[i] == kws[j]) { aantal++; }
    }
  }
  
  kwd = Math.round(aantal / woorden.length * 10000) / 100
  
  var msg = "<p><strong>" + aantal + " op de " + woorden.length + " woorden betekent een keyword density van " + kwd + "%</strong></p>";

  if (kwd < 2)
  { msg += "<p style='text-align: center'><span style=background-color:#ff0000;>Te weinig, houd 2% tot 5% aan...</span></p>"; }
  if ((kwd >= 2) && (kwd <= 5))
  { msg += "<p style='text-align: center'><span style=background-color:#00FF00;>Goed</span></p>"; }
  if (kwd > 5)
  { msg += "<p style='text-align: center'><span style=background-color:#FF9900;>Te veel, houd 2% tot 5% aan...</span></p>"; }
  
  
  for (var j = 0; j < kws.length; j++)
  {
    var reg = new RegExp(kws[j], "gi");
    origtxt = origtxt.replace(reg, "<span style='background-color:#63D3F7'>" + kws[j] + "</span>");
  }
  
  document.getElementById("resultaat").innerHTML = msg + origtxt + "<br><br>";
  document.getElementById("uitleg").style.display = "block";
  
  pageTracker._trackPageview('keyword-density-tool');
}