serverfiles/openwrt/common/opt/lib/resources/admin/admin.js

(function() {

/*
 * seems like there is not need to use getElementById
 * and instead access elements directly by their id
 */

//  var uploadbtn = document.getElementById('uploadbtn');
//  var uploadfile = document.getElementById('uploadfile')
  uploadbtn.addEventListener('change', function () {
    uploadfile.value = this.value.replace(/^.*\\/, "");
    var len = uploadfile.value.length - 7;
    uploadfile.setAttribute('size', len);
    var len = uploadfile.offsetWidth;
    uploadbtn.style.width = len + "px";
  });

  var selects = wan.getElementsByTagName('select');
  for (i = 0; i < selects.length; i++) { 
    wanChange(selects[i]);
  }

  wanconf.addEventListener('change', function() { wanChange(event.target) });

  function wanChange(e) {
  //  var wanwifi = document.getElementById('wanwifi');
  //  var wanaddr = document.getElementById('wanaddr');
    switch (e[e.selectedIndex].id) {
      case 'wlan':
        wanwifi.setAttribute('class','show');
        break;
      case 'dhcp':
        wanaddr.setAttribute('class','hide');
        break;
      case 'eth':
        wanwifi.setAttribute('class','hide');
        break
      case 'stat':
        wanaddr.setAttribute('class','show');
        break;
    }
  }

})();

/*
function formChange() {
  if (document.activeElement.tagName.toLowerCase() !=  'select') {
    console.log('not select');
    return false;
  }
  aElem = document.activeElement;
  aParent = aElem.parentElement;
  sOpt = aElem[aElem.selectedIndex];
  console.log(aElem.id + sOpt.id);
  if (aElem.id + sOpt.id == 'wanprotostat') {
    document.getElementById('wanaddr').setAttribute('class','show');
  }
  if (aElem.id + sOpt.id == 'wanprotodhcp') {
    document.getElementById('wanaddr').setAttribute('class','hide');
  }
  if (aElem.id + sOpt.id == 'wanifnamewlan') {
    document.getElementById('wanwifi').setAttribute('class','show');
  }
  if (aElem.id + sOpt.id == 'wanifnameeth') {
    document.getElementById('wanwifi').setAttribute('class','hide');
  }
};
*/