function check(checkbox) {
for (i = 0; i < checkbox.length; i++) {
checkbox[i].checked = true;
}
return "Select all";
}

function uncheck(checkbox) {
for (i = 0; i < checkbox.length; i++) {
checkbox[i].checked = false;
}
return "Select none";
}

function isEmail(str) {
  // are regular expressions supported?
  var supported = 0;
  if (window.RegExp) {
    var tempStr = "a";
    var tempReg = new RegExp(tempStr);
    if (tempReg.test(tempStr)) supported = 1;
  }
  if (!supported) 
    return (str.indexOf(".") > 2) && (str.indexOf("@") > 0);
  var r1 = new RegExp("(@.*@)|(\\.\\.)|(@\\.)|(^\\.)");
  var r2 = new RegExp("^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$");
  return (!r1.test(str) && r2.test(str));
}
function checkImage(myform) {
  var ext = myform.userfile.value;
  ext = ext.substring(ext.length-3,ext.length);
  ext = ext.toLowerCase();
  if(ext != 'jpg' && ext != 'jpeg' && ext != 'gif' && ext != 'png') {
	  myform.imgShow.src  = 'images/transparant.gif';
    alert('You did not select a picture!');
    return false; }
  else
  	myform.imgShow.src  = myform.userfile.value ;
    return true; 
}

function EditCounter(myform, aantalChar){
		var elements = document.getElementsByTagName('textarea');
		if (elements[0].value.length >= aantalChar){
			elements[0].value = String(elements[0].value).substring(0,aantalChar)
			myform.txtCounter.value =aantalChar   - elements[0].value.length   ;
		}else{
			myform.txtCounter.value = aantalChar - elements[0].value.length ;
		}
}
function validate_comment(myform) {
	txtName=myform.txtnaam.value;
	txtComments=myform.txtComments.value;
	txtSpam=myform.security_code.value;
	if (txtName=='' || txtComments==''|| txtSpam == '' ) {
	alert('Velden verplicht in te vulden !');
		return false;
	}
}

function validate_contact(myform) {
	txtName=myform.txtName.value;
	txtEmail=myform.txtEmail.value;
	txtSecurity_code=myform.security_code.value;

	if ((txtName == '') || (txtEmail == '') || (txtSecurity_code == '') || (!isEmail(txtEmail))){
	alert('Het is verplicht alle velden correct in te vullen !');
		return false;
	}
return true;
}