Super simple super tiny ajax function

gistfile1.js

function xhr(url, post) {
    var req = window.ActiveXObject
        ? new ActiveXObject('Microsoft.XMLHTTP')
        : new XMLHttpRequest();
    if (post) {
        req.open("POST", url, true);
        req.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
        req.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
        req.setRequestHeader('Connection', 'close');
        req.send(post);
        return;
    }
    req.open("GET", url, true);
}