ajax读取头信息

jQuery

$.get(url, function(data, statusTest, xhr){
    console.log(xhr);
    console.log(xhr.getAllResponseHeaders());//获取所有的响应头消息
    //console.log(xhr.getResponseHeader('server'));//获取服务器信息   
    let type =  xhr.getResponseHeader("content-type")  //获取content-type
});

原生ajax

function createXmlHttp() {
    var xmlhttp = null;
    if (window.XMLHttpRequest)
    {// code for IE7+, Firefox, Chrome, Opera, Safari
      xmlhttp = new XMLHttpRequest();
    }else{// code for IE6, IE5
      xmlhttp = new ActiveXO相应bject("Microsoft.XMLHTTP");
    }
    return xmlhttp;  
}
var xmlhttp = createXmlHttp();
xmlhttp.open("GET", url, true);
xmlhttp.send();
xmlhttp.onreadystatechange=function(){//设置状态发生变化时候监听函数
    if(xmlhttp.readyState ==4 && 200 == xmlhttp.status){
        console.log(xmlhttp.getAllResponseHeaders());//获取所有的响应头消息
        //console.log(xmlhttp.getResponseHeader('server')); //获取服务器信息        
    }
}