//global variables that can be used by ALL the function son this page.
var inputs;
var imgFalse = 'images/aa.png';
var imgTrue = 'images/bb.png';

//this function runs when the page is loaded, put all your other onload stuff in here too.
function init() {
    replaceChecks();
}

function replaceChecks() {
    
    //get all the input fields on the page
    inputs = document.getElementsByTagName('input');

    //cycle trough the input fields
    for(var i=0; i < inputs.length; i++) {

        //check if the input is a checkbox
        if(inputs[i].getAttribute('type') == 'checkbox') {
            
            //create a new image
            var img = document.createElement('img');
            
            //check if the checkbox is checked
            if(inputs[i].checked) {
                img.src = imgTrue;
            } else {
                img.src = imgFalse;
            }

            //set image ID and onclick action
            img.id = 'checkImage'+i;
            //set image
            img.onclick = new Function('checkChange('+i+')');
            //place image in front of the checkbox
            inputs[i].parentNode.insertBefore(img, inputs[i]);
            
            //hide the checkbox
            inputs[i].style.display='none';
        }
    }
}

//change the checkbox status and the replacement image
function checkChange(i) {

    if(inputs[i].checked) {
        inputs[i].checked = '';
        document.getElementById('checkImage'+i).src=imgFalse;
    } else {
        inputs[i].checked = 'checked';
        document.getElementById('checkImage'+i).src=imgTrue;
    }

    // toevoeging, slechts 1 aanvinking mogelijk
    if(inputs[i].getAttribute('id') != 'vw') {
      //get all the input fields on the page
      inputs = document.getElementsByTagName('input');

      //cycle trough the input fields
      for(var l=0; l < inputs.length; l++) {
        if(inputs[l].getAttribute('type') == 'checkbox' && inputs[l].getAttribute('id') != 'vw' && l != i) {
          document.getElementById('checkImage'+l).src=imgFalse;
          inputs[l].checked = '';
        }
      }
    }
}




    function selectReplacement(obj) {
      // append a class to the select
      obj.className += ' replaced';
      // create list for styling
      var ul = document.createElement('ul');
      ul.className = 'selectReplacement';
      var opts = obj.options;
      for (var i=0; i<opts.length; i++) {
        var selectedOpt;
        if (opts[i].selected) {
          selectedOpt = i;
          break;
        } else {
          selectedOpt = 0;
        }
      }
      for (var i=0; i<opts.length; i++) {
        var li = document.createElement('li');
        var txt = document.createTextNode(opts[i].text);
        li.appendChild(txt);
        li.selIndex = opts[i].index;
        li.selectID = obj.id;
        li.onclick = function() {
          selectMe(this);
        }
        if (i == selectedOpt) {
          li.className = 'selected';
          li.onclick = function() {
            this.parentNode.className += ' selectOpen';
            this.onclick = function() {
              selectMe(this);
            }
          }
        }
        if (window.attachEvent) {
          li.onmouseover = function() {
            this.className += ' hover';
          }
          li.onmouseout = function() {
            this.className = 
              this.className.replace(new RegExp(" hover\\b"), '');
          }
        }
        ul.appendChild(li);
      }
      // add the input and the ul
      obj.parentNode.appendChild(ul);
    }
    function selectMe(obj) {
      var lis = obj.parentNode.getElementsByTagName('li');
      for (var i=0; i<lis.length; i++) {
        if (lis[i] != obj) { // not the selected list item
          lis[i].className='';
          lis[i].onclick = function() {
            selectMe(this);
          }
       } else {
          setVal(obj.selectID, obj.selIndex);
          obj.className='selected';
          obj.parentNode.className = 
            obj.parentNode.className.replace(new RegExp(" selectOpen\\b"), '');
          obj.onclick = function() {
            obj.parentNode.className += ' selectOpen';
            this.onclick = function() {
              selectMe(this);
            }
          }
        }
      }
    }
    function setVal(objID, selIndex) {
      var obj = document.getElementById(objID);
      obj.selectedIndex = selIndex;
    }
    function setForm() {
      var s = document.getElementsByTagName('select');
      for (var i=0; i<s.length; i++) {
        selectReplacement(s[i]);
      }
    }
    function closeSel(obj) {
      // close the ul
    }
    window.onload = function() {replaceChecks();
      (document.all && !window.print) ? null : setForm();
    }