function  isUrenPerDag(entry) {
      if (isNaN(entry.value)) {
            alert(isUrenPerDag_1);
            entry.value="";
      } 
	  if (entry.value > 24) {
            alert(isUrenPerDag_2);
			entry.value="";
      }
	  if (entry.value < 0) {
            alert(isUrenPerDag_3);
			entry.value="";
      }
}
function  isANumber(veld) {
      if (isNaN(veld.value)) {
            alert(isANumber_1);
            veld.value = "";
			return false;
      }
	  return true;
}
function  isAnInteger(veld) {
      if (!(parseInt(veld.value) == veld.value)) {
            alert(isAnInteger_1);
            veld.value = "";
      }
}
function  isAPositiveInteger(veld) {
	if(veld.value!='')
	{
      if ((!(parseInt(veld.value) == veld.value)) || (veld.value < 0)) {
            alert(isAPositiveInteger_1);
            veld.value = "";
      }
	}
}
function  isAPercentage(veld) {
	if (isNaN(veld.value)) {
    	alert(isANumber_1);
		veld.value = "";
		}
    if ((veld.value < 0) || (veld.value > 100)) {
		alert('Dit is geen geldig percentage (getal tussen 0 en 100)');
		veld.value = "";
	}
}
function  isADate(veld) {
      if ((!(!(isNaN(veld.value.substring(0,4))) && (veld.value.substring(4,5) == "-") && !(isNaN(veld.value.substring(5,7))) && (veld.value.substring(7,8) == "-") && !(isNaN(veld.value.substring(8,10))))) && (veld.value != ''))                         
      {
            alert(isDatum_1);
            veld.value="";
      }
}
function  isDatum(entry) {
      if ((!(!(isNaN(entry.substring(0,4))) && (entry.substring(4,5) == "-") && !(isNaN(entry.substring(5,7))) && (entry.substring(7,8) == "-") && !(isNaN(entry.substring(8,10))))) && (entry != ''))                         
      {
            alert(isDatum_1);
            entry="";
      }
}
function isTijd(veld){
	if (veld.value != ''){
		if (veld.value.length == 4)
		{veld.value = veld.value.substring(0,2)+':'+veld.value.substring(2,4)
		}
		if ((!(veld.value.substring(0,1) == '0' || veld.value.substring(0,1) == '1' || veld.value.substring(0,1) == '2')) || (!(veld.value.substring(1,2) >= 0 && veld.value.substring(1,2) <= 9)) || (!(veld.value.substring(3,4) >= 0 && veld.value.substring(3,4) <= 5)) || (!(veld.value.substring(4,5) >= 0 && veld.value.substring(4,5) <= 9)) || (veld.value.charAt(2) != ':') || (veld.value.length != 5)) {
			alert(isTijd_1);
			veld.value="";
			veld.focus();
		}
	}
}
function isCode(veld)
{
	var tekens = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-"
	var ok = "yes"
	code = veld.value;
	for (var i=0; i < code.length; i++) 
	{
		var temp = code.charAt(i);
		if (tekens.indexOf(temp) == "-1") {ok = "no"};
	}
		if (ok == "no")
	{
		alert(isCode_1);
		veld.value = "";	
	}
}
function isWachtwoord(veld)
{
	var tekens = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-"
	var ok = "yes"
	code = veld.value;
	for (var i=0; i < code.length; i++) 
	{
		var temp = code.charAt(i);
		if (tekens.indexOf(temp) == "-1") {ok = "no"};
	}
		if (ok == "no")
	{
		alert(isWachtwoord_1);
		veld.value = "";	
	}
}