var DataLoader = {
    xhr: new XMLHttpRequest,
    load: function(url, callback, method) {
        this.xhr.onload = callback;
        this.xhr.open(method || 'GET', url);
        this.xhr.send();
    }
};

function show_data(evt) {
    var xhr = evt.target;
    document.body.innerHTML += '<pre>' + xhr.response + '</pre>';
};

DataLoader.load('https://api.github.com/users/o0', show_data);
DataLoader.load('https://api.github.com/users/zeckson', show_data);