js写个原生的ajax过程.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    window.onload=function(){
        document.getElementsByTagName('a')[0].onclick=function(){
            if (window.XMLHttpRequest){
                var xmlhttp=new XMLHttpRequest();
            }else{
                var xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
            }
            var method='GET';
            var url=this.href;
            xmlhttp.open(method,url);
            xmlhttp.send();
            xmlhttp.onreadystatechange=function(){
                if(xmlhttp.readyState==4){
                    if(xmlhttp.status==200||xmlhttp.status==304){
                        var txt=xmlhttp.responseText;
                        var json=eval('('+txt+')');
                        document.getElementById('name').innerHTML='姓名'+json.ruei.name;
                        document.getElementById('age').innerHTML='年龄'+json.ruei.age;
                        document.getElementById('job').innerHTML='工作'+json.ruei.job;
                    }
                }
            }
            return false;
        }
    }
</script>
</body>
</html>