原生ajax操作

javascript知识点

var req = new XMLHttpRequest();
req.onreadystatechange = function () {
    if(req.readyState ===4){
        var responseHeaders = req.getAllResponseHeaders();//获取响应头信息
        var data = req.responseText;//获取数据
    }
}
req.open('GET',url+'?'+params.join("&"),true);
req.setRequestHeader('X-Requested-Width','XMLHttpRequest');//设置请求头信息
req.send(null);