IE和火狐兼容的AJAX写法

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","text/xml");   req.setRequestHeader("Content-Type","gb2312");  }catch(e){   try {    req = new ActiveXObject("Microsoft.XMLHTTP");   }catch (e){}  }

  req = new ActiveXObject("Microsoft.XMLHTTP");

  if (req) {   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);     }    }   }   req.open("POST", url, true);

   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);  }

 }}