AJAX原生JS代码

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");
  }
 }
}