ajax例子

var xmlHttp;/**XMLHttpRequest  */function createXMLHttpRequest(){   if(window.XMLHttpRequest) {          xmlHttp = new XMLHttpRequest();          } else if (window.ActiveXObject) {           xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");       } else {           xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");       }     }/**ajax 执行方法 传入要访问后台地址，该方法会将返回结果传给callback()方法*/function executeAjax(url){   createXMLHttpRequest();   xmlHttp.abort() ;   xmlHttp.open("post",url,true);   xmlHttp.onreadystatechange = function(){     if(xmlHttp.readyState==4){      if(xmlHttp.status==200) {          callback(xmlHttp.responseText);      }     }   };    xmlHttp.send(null);}function executeAjaxFun(url,fun){   createXMLHttpRequest();   xmlHttp.abort();   xmlHttp.open("post",url,true);   xmlHttp.onreadystatechange = function(){     if(xmlHttp.readyState==4){      if(xmlHttp.status==200) {          fun(xmlHttp.responseText);      }     }   };    xmlHttp.send(null);}