How to migrate a .change function from jQuery to plain Javascript
<select id="faq" class="onchance_fill">...</select>
  <select id="pages" class="onchance_fill">...</select>
  <select id="faq" class="onchance_fill">...</select>

<input type="text" onchange="selectByValue(this.form,'linklisthref',this.value);" value="" class="mceFocus" name="href" id="href" style="width: 260px;">

$('.ajax_onchance_fill').change(function() {
        data = $('.ajax_onchance_fill').val();
        $('#href').text(data);
    });

<script type="text/javascript">
  function load() {
  var elements = document.getElementsByClassName('onchance_fill');
  for(e in elements){
      elements[e].onchange = function(){
          document.getElementById('href').value = this.value;
     }
  }
  }
</script>

document.getElementsByClassName("ajax_onchance_fill").onchange = function() {
   getElementById('href').value = this.options[this.selectedIndex].text;
};

$('.ajax_onchance_fill').change(function() {
        var data = $(this).val();
        $('#mytextboxid').val(data);
    });