IE和Firefox相容的AJAX寫法

方法一：

function gethttp(sid, url){
 var xmlHttp;
 if (window.ActiveXObject) {
  xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
 }
 else if (window.XMLHttpRequest) {
  xmlHttp = new XMLHttpRequest();
 }
 
 xmlHttp.onreadystatechange = function(){
  if(xmlHttp.readyState == 4){
   document.getElementById(sid).innerHTML = xmlHttp.responseText;
  }
 }

 xmlHttp.open("POST",url,true);
 xmlHttp.send(null);
}

方法二：

function gethttp(sid, url){
 if (window.XMLHttpRequest) {
  var req = new XMLHttpRequest();
  if (req.overrideMimeType) {
   req.overrideMimeType(''text/html'');
  }
  req.onreadystatechange = function(){
   if (req.readyState == 4) {
    if (req.status == 200) {
     alert(id+" "+req.responseText);
     document.getElementById(sid).innerHTML = req.responseText;
    }
    else {
     alert("Problem with server response:  "+ req.statusText);
    }
   }
  }

  try {
   req.open("POST", url, true);
  }
  catch (e) {
   alert("Server Communication Problem "+e);
  }

  req.setRequestHeader("Cache-Control","no-cache");
  req.setRequestHeader("If-Modified-Since",new Date(0));
  req.setRequestHeader("Content-length", url.length);
  req.setRequestHeader("Connection", "close");

  req.send(null);
 }
 else
 if (window.ActiveXObject) {

  try{
   var req = new ActiveXObject("Msxml2.XMLHTTP");
   req.setRequestHeader("Content-Type",</