ajax script

this is basic of ajax code.
(ajax.js)

  var xmlhttp = false;

  //check if using IE

  try {
    //check if IE > IE 5
    xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
  } catch (e) {
    //use activeX
    try {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (E) {
      xmlhttp = false;
    }
  }

  //check if not using IE
  if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {
    xmlhttp = new XMLHttpRequest();
  }
  //function request
  function makeRequest ( serverPage, objID, msgLoad ) {
    var obj = document.getElementById(objID);
    var msg = msgLoad;
    xmlhttp.open("GET", serverPage);
    xmlhttp.onreadystatechange = function() {
      if ( xmlhttp.readyState == 4 && xmlhttp.status == 200 ) {
        obj.innerHTML = xmlhttp.responseText;
      } else {
      obj.innerHTML = "<br /><br /><div align ='center'><img src='images/ajax.gif' alt='Loading' /><br />"+msg + "</div>";
      }
    }
    xmlhttp.send(null);
  }
  //function download
  function download ( serverPage, objID, msgLoad ) {
    var obj = document.getElementById(objID);
    var msg = msgLoad;
    xmlhttp.open("GET", serverPage);
    xmlhttp.onreadystatechange = function() {
      if ( xmlhttp.readyState == 4 && xmlhttp.status == 200 ) {
        window.location = serverPage;
      } else {
        obj.innerHTML = "<br /><br /><div align ='center'><img src='images/ajax.gif' alt='Loading' /><br />"+msg + "</div>";
      }
    }
    xmlhttp.send(null);
  }
  //function for search
  function searchRequest ( serverPage, objID, msgLoad, formName , getcari ) {
    var obj = document.getElementById(objID);
    var msg = msgLoad;
    var cari = document.forms[formName].elements[getcari].value;
    var t = new Date()
  
    xmlhttp.open("GET", serverPage+"?search="+cari+"&t="+t.getTime());
    xmlhttp.onreadystatechange = function() {
      if ( xmlhttp.readyState == 4 && xmlhttp.status == 200 ) {
        obj.innerHTML = xmlhttp.responseText;
      } else {
        obj.innerHTML = "<br /><br /><div align ='center'><img src='images/ajax.gif' alt='Loading' /><br />"+msg + "</div>";
      }
    }
    xmlhttp.send(null);
  }