Question : selecting values in a select box multiple

i have one select box and want to select 5 values @ a time, if values exceed more than 5, it show popup and error! only 5 allowed! please guide

Answer : selecting values in a select box multiple

My version

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<script>
var maxSel = 3;
var selected =[];
window.onload=function() {
  saveSel(document.getElementById('sel')); // initialise
}
function saveSel(sel) {
  for (var i=0;i<sel.options.length;i++) {
    selected[i]=(sel.options[i].selected); 
  }
}
function resetSel(sel) {
  for (var i=0;i<sel.options.length;i++) {
    sel.options[i].selected = selected[i]; 
  }
}
function test(sel) {
  for (var i=0,newCnt=0;i<selected.length;i++) {
    newCnt+= (sel.options[i].selected)?1:0;
  }
  if (newCnt>maxSel) {
    alert('Sorry, you can only select a maximum of '+maxSel);
    resetSel(sel);
  }
  else saveSel(sel); // store the new 
}

</script>
<select id='sel' multiple onChange="test(this)">
<option value='1'>One</option>
<option value='2'>Two</option>
<option value='3'>Three</option>
<option value='4'>Four</option>
<option value='5'>Five</option>
</select>