确定AJAX是否可行?

var xhr;
if (window.XMLHttpRequest) {
    xhr = new XMLHttpRequest();
}
else if (window.ActiveXObject) {
    try {
        xhr = new ActiveXObject("Msxml2.XMLHTTP");
    } catch(err) { 

    }
}
else {
    //It couldn't find any of those Ajax objects
}

if(!xhr) {
    //Here you know now that Ajax is not possible with this client
}

更新:

试试…杰森·怀亚特建议的接球。我错过了。

而且,这让我想起了一个 bad example from The Daily WTF