var http_request = false; function send_request(method,url,content,responseType,callback){
   http_request = false;  if(window.XMLHttpRequest) { //现代浏览器   http_request = new XMLHttpRequest();   if(http_request.overrideMimeType) {
     http_request.overrideMimeType("text/xml");   }  } else if(window.ActiveXObject) { //老IE浏览器   try{
     http_request = new ActiveXObject("Msxml2.XMLHTTP");   } catch(e) {
     try {
      http_request = new ActiveXObject("Microsoft.XMLHTTP");    } catch(e) {}   }  }  if(!http_request) {
    window.alert("Can't create XMLHttpRequest");   return false;  }  if(responseType.toLowerCase() == "text") {
    //http_request.onreadystatechange = processTextResponse;   http_request.onreadystatechange = callback;  } else if(responseType.toLowerCase == "xml") {
    //http_request.onreadystatechange = processXMLResponse;   http_request.onreadystatechange = callback;  } else {
    window.alert("error");   return false;  }  if(method.toLowerCase() == "get") {
    http_request.open(method, url, true);  } else if(method.toLowerCase() == "post") {
    http_request.open(method, url, true);   http_request.setRequestHeader("content-Type","application/x-www-form-urlencoded");  } else {
    window.alert("http request error");   return false;  }  http_request.send(content); } function processTextResponse() {
   if(http_request.readyState == 4) {
    if(http_request.status == 200) {
     alert(http_request.responseText);   } else {
     alert("request error");   }  } } function processXMLResponse() {
   if(http_request.readyState == 4) {
    if(http_request.status == 200) {
     alert(http_request.responseXML);   } else {
     alert("request error");   }  } }