参考:http://book.youkuaiyun.com/bookfiles/11/10011443.shtml 创建XMLHttpRequest对象的一个实例 function callback() ...{ if (xmlHttp.readyState == 4) ...{ if (xmlHttp.status == 200) ...{ //do something interesting here } }} var xmlHttp;function validateEmail() ...{ var email = document.getElementById("email"); var url = "validate?email=" + escape(email.value); if (window.ActiveXObject) ...{ xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } else if (window.XMLHttpRequest) ...{ xmlHttp = new XMLHttpRequest(); }xmlHttp.open("GET", url);xmlHttp.onreadystatechange = callback;xmlHttp.send(null);}