如果它与调用函数位于同一服务器上，则可以使用XMLHttpRequest-

If it's on the same server as your calling function you can use XMLHttpRequest-

此示例不是异步的，但是您可以根据需要进行创建.

This example is not asynchronous, but you can make it so if you wish.

function fetchHeader(url, wch) {
    try {
        var req=new XMLHttpRequest();
        req.open("HEAD", url, false);
        req.send(null);
        if(req.status== 200){
            return req.getResponseHeader(wch);
        }
        else return false;
    } catch(er) {
        return er.message;
    }
}

alert(fetchHeader(location.href,'Last-Modified'));