Minimal jQuery Replacement

jquery.min.js

/**
 * Minimal jQuery replacement
 */
 (function () {
    'use strict';

     var find = function (element) {
        return function (query) {
            var results = element.querySelectorAll(query),
                result;
            
            if (results.length === 1) {
                result = extend(results[0])
                return result;
            }
            
            results = Array.prototype.slice.call(results);

            results.forEach(function (result) {
                result = extend(result);
            });
            
            return results;
        }
    },

    addClass = function (element) {
        return function (newClass) {
            var css = element.className.split(' '),
                newClass = newClass.split(' ');

            newClass.forEach(function (name) {
                if (css.indexOf(name) > -1) {
                    return;
                }
                css.push(name);
            });

            element.className = 
                css.filter(function (name) {
                        return name !== '';
                    })
                    .join(' ')
                    .trim();

            return element;
        }
    },

    removeClass = function (element) {
        return function (oldClass) {
            var css = element.className.split(' '),
                oldClass = oldClass.split(' ');

            oldClass.forEach(function (name) {
                var index = css.indexOf(name);

                if (index === -1) {
                    return;
                }

                delete css[index];
            });

            element.className = 
                css.filter(function (name) {
                        return name !== '';
                    })
                    .join(' ')
                    .trim();

            return element;
        }
    },

    extend = function (element) {
        element.find = find(element);
        element.addClass = addClass(element);
        element.removeClass = removeClass(element);

        return element;
    };

    window.$ = extend(document);
 })()