原生js版ajax请求

    function getXMLHttpRequest() {
              var xhr;
              if(window.ActiveXObject) {
                       xhr= new ActiveXObject("Microsoft.XMLHTTP");
              }else if (window.XMLHttpRequest) {
                       xhr= new XMLHttpRequest();
              }else {
                       xhr= null;
              }
              return xhr;
    }  

    function save() {
              var xhr = getXMLHttpRequest();
              xhr.open("post","url");
              var data = "name=mikan&address=street...";
              xhr.send(data);
              xhr.onreadystatechange= function() {
                       if(xhr.readyState == 4 && xhr.status == 200) {
                                alert("returned:"+ xhr.responseText);
                       }
              };
    }