//Ajax XMLHttpRequest Object 생성하기 (1)
function createHttpRequestObject(){
var xmlObj;
  try {
    // Firefox, Opera 8.0+, Safari
    xmlObj = new XMLHttpRequest();
  } catch (e){
    // Internet Explorer
    try {
    xmlObj = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (e) {
      try  {
      xmlObj = new ActiveXObject("Microsoft.XMLHTTP");
      } catch (e) {
        alert("Your browser does not support AJAX!");
        xmlObj = null;
      }
    }
  }
  return xmlObj;
}

//Ajax XMLHttpRequest Object 생성하기 (2)
function getXMLHTTPRequest() {
var request = false;
  try {
  // Firefox, Opera 8.0+, Safari
  request = new XMLHttpRequest();
  }
  catch (err1) {
    // Internet Explorer
    try {
      request = new ActiveXObject("Msxml2.XMLHTTP");
    }
    catch (err2) {
      try {
        request = new ActiveXObject("Microsoft.XMLHTTP");
      }
      catch (err3) {
        request = false;
      }
    }
  }
  return request
}

//Ajax XMLHttpRequest Object 생성하기 (3)
//브라우저 종류 판별을 이용한 방법
function getXMLHTTPRequest1() {
var request = false;
  if (window.ActiveXObject) {
    try {
      request = new ActiveXObject("Msxml2.XMLHTTP");
    } catch(e) {
        try {
          request = new ActiveXObject("Microsoft.XMLHTTP");
        } catch(e1) {
          request = false;
        }
    }
  } else if (window.XMLHttpRequest) {
      request = new XMLHttpRequest();
  } else {
      request = false;
  }
  return request;
}