A super simple JS framework. Firefox 3.1+, IE8+, Safari 3.1+ only.

framework.js

// ==ClosureCompiler==
// @output_file_name framework_min.js
// @compilation_level ADVANCED_OPTIMIZATIONS
// ==/ClosureCompiler==

(function() {
    var docProto = Document.prototype,
        htmlElementProto = HTMLElement.prototype,
        nodeListProto = NodeList.prototype;

    function qs(query) {
        return this.querySelector(query);
    }

    function qsa(query) {
        return this.querySelectorAll(query);
    }

    docProto['qs'] = qs;
    docProto['qsa'] = qsa;

    htmlElementProto['qs'] = qs;
    htmlElementProto['qsa'] = qsa;

    htmlElementProto['computeStyle'] = function(prop) {
        return window.getComputedStyle(this, null).getPropertyValue(prop).split('px').join('');
    }

    htmlElementProto['addClass'] = function(className) {
        this.className = (this.className.split(className).join('') + ' ' + className)['trim']();
        return this;
    }

    htmlElementProto['removeClass'] = function(className) {
        this.className = this.className.split(className).join('')['trim']();
        return this;
    }

    nodeListProto['addClass'] = function(className) {
        for (var i = 0; i < this.length; ++i) {
            this[i]['addClass'](className);
        }
    }

    nodeListProto['removeClass'] = function(className) {
        for (var i = 0; i < this.length; ++i) {
            this[i]['removeClass'](className);
        }
    }

    window['XHR'] = (function() {
        function parseResponse(responseText) {
            try {
                return JSON.parse(responseText);
            }
            catch (error) {
                return responseText;
            }
        }

        function request(method, url, data, callback) {
            var req = new XMLHttpRequest();
            req.open(method, url, !!callback);

            if (!!callback) {
                req.onreadystatechange = function(e) {
                    if (req.readyState === 4 && req.status === 200) {
                        callback(parseResponse(req.responseText));
                    }
                }
            }

            req.send(data);

            return (!!callback) ? null : parseResponse(req.responseText);
        }

        return {
            'get': function(url, callback) {
                return request('GET', url, null, callback);
            },

            'post': function(url, data, callback) {
                return request('POST', url, data, callback);
            }
        }
    }());

}());