a simple err-first callback function to make a GET request with jQuery, XHR, or Node.js

get.js

function get(url, cb) {
    // use jQuery if you can, if not, XHR, or try to node
    if (typeof $ !== "undefined" && !!$().jquery) {
        $.ajax(url).then(function(data) {
            cb(null, data);
        }, function(j, t, e) {
            cb(e);
        });
    } else if (typeof XMLHttpRequest !== "undefined") {
        // simple XHR attempt
        var xhr = new XMLHttpRequest();
        xhr.onload = function() { if (xhr.response) cb(null, xhr.response); }
        xhr.onerror = function(e) { cb(e); }
        xhr.open('get', url, true);
        xhr.send();
    } else if (typeof module !== "undefined" && typeof require !== "undefined") {
        // reckless module require based on protocol.. good luck
        var protocol = require(url.split('://')[0]);
        protocol.get(url, function(res) {
            var response = "";
            res.on('data', function(d) { response += d; });
            res.on('end', function(d) {
                response += d;
                if (response) cb(null, response);
            });
        }).on('error', cb);
    } else {
        cb("No transport discovered");
    }
}