DOM manipulation

/*
Create a module for working to work with DOM. The module should have the following functionality

    Add element to parent element by given selector
    Remove element from the DOM  by given selector
    Attach event to given selector by given event type and event hander
    Add elements to buffer, which appends them to the DOM when their for some selector count becomes 100
    The buffer contains elements for each selector it gets
    Get elements by CSS selector
    The module should reveal only the methods */

'use strict';

var domModul = (function () {
    // Fields
    var _parentNode;
    var _currentNode;
    var _childNode;
    var _childNodeSet;
    var _buffer = [];

    // Private functions
    function getElement(selector) {
        return document.querySelector(selector);
    }
    function getElementsAll(selector) {
        return document.querySelectorAll(selector);
    }

    // Public functions
    return {
        appendChild: function (element, selector) {
            _parentNode = getElement(selector);
            _parentNode.appendChild(element);
        },
        removeChild: function (parentSelector,childSelector) {
            _parentNode = getElement(parentSelector);
            _childNode = _parentNode.querySelector(parentSelector + ">" + childSelector);
            _parentNode.removeChild(_childNode);
        },
        removeAllChild: function (parentSelector, childSelector) {
            _parentNode = getElement(parentSelector);
            _childNodeSet = document.querySelectorAll(parentSelector + ">" + childSelector);
            for (var i = 0; i < _childNodeSet.length; i++) {
                if (_childNodeSet[i].nodeType === 1) {
                    _childNodeSet[i].parentNode.removeChild(_childNodeSet[i]);
                }
            }
        },
        attachEvent: function (elementSelector, eventType, eventHandler) {
            _currentNode = getElement(elementSelector);
            _currentNode.addEventListener(eventType, eventHandler);
        },
        addToBuffer: function (parentSelector, element) {
            if (_buffer[parentSelector] === undefined) {
                _buffer[parentSelector] = document.createDocumentFragment();
                _buffer[parentSelector].appendChild(element);
            } else {
                _buffer[parentSelector].appendChild(element);
                if (_buffer[parentSelector].childNodes.length >= 100) {
                    _parentNode = getElement(parentSelector);
                    _parentNode.appendChild(_buffer[parentSelector]);
                }
            }
        },
        cssSelector: function (selector) {
            return getElement(selector);
        },
        cssSelectorAll: function (selector) {
            return getElementsAll(selector);
        }
    };
}());