The source code

    /**
     * @class Ext.DomHelper
     * <p>The DomHelper class provides a layer of abstraction from DOM and transparently supports creating
     * elements via DOM or using HTML fragments. It also has the ability to create HTML fragment templates
     * from your DOM building code.</p>
     *
     * <p><b><u>DomHelper element specification object</u></b></p>
     * <p>A specification object is used when creating elements. Attributes of this object
     * are assumed to be element attributes, except for 4 special attributes:
     * <div class="mdetail-params"><ul>
     * <li><b><tt>tag</tt></b> : <div class="sub-desc">The tag name of the element</div></li>
     * <li><b><tt>children</tt></b> : or <tt>cn</tt><div class="sub-desc">An array of the
     * same kind of element definition objects to be created and appended. These can be nested
     * as deep as you want.</div></li>
     * <li><b><tt>cls</tt></b> : <div class="sub-desc">The class attribute of the element.
     * This will end up being either the "class" attribute on a HTML fragment or className
     * for a DOM node, depending on whether DomHelper is using fragments or DOM.</div></li>
     * <li><b><tt>html</tt></b> : <div class="sub-desc">The innerHTML for the element</div></li>
     * </ul></div></p>
     *
     * <p><b><u>Insertion methods</u></b></p>
     * <p>Commonly used insertion methods:
     * <div class="mdetail-params"><ul>
     * <li><b><tt>{@link #append}</tt></b> : <div class="sub-desc"></div></li>
     * <li><b><tt>{@link #insertBefore}</tt></b> : <div class="sub-desc"></div></li>
     * <li><b><tt>{@link #insertAfter}</tt></b> : <div class="sub-desc"></div></li>
     * <li><b><tt>{@link #overwrite}</tt></b> : <div class="sub-desc"></div></li>
     * <li><b><tt>{@link #createTemplate}</tt></b> : <div class="sub-desc"></div></li>
     * <li><b><tt>{@link #insertHtml}</tt></b> : <div class="sub-desc"></div></li>
     * </ul></div></p>
     *
     * <p><b><u>Example</u></b></p>
     * <p>This is an example, where an unordered list with 3 children items is appended to an existing
     * element with id <tt>'my-div'</tt>:<br>
     <pre><code>
    var dh = Ext.DomHelper; // create shorthand alias
    // specification object
    var spec = {
        id: 'my-ul',
        tag: 'ul',
        cls: 'my-list',
        // append children after creating
        children: [     // may also specify 'cn' instead of 'children'
            {tag: 'li', id: 'item0', html: 'List Item 0'},
            {tag: 'li', id: 'item1', html: 'List Item 1'},
            {tag: 'li', id: 'item2', html: 'List Item 2'}
        ]
    };
    var list = dh.append(
        'my-div', // the context element 'my-div' can either be the id or the actual node
        spec      // the specification object
    );
     </code></pre></p>
     * <p>Element creation specification parameters in this class may also be passed as an Array of
     * specification objects. This can be used to insert multiple sibling nodes into an existing
     * container very efficiently. For example, to add more list items to the example above:<pre><code>
    dh.append('my-ul', [
        {tag: 'li', id: 'item3', html: 'List Item 3'},
        {tag: 'li', id: 'item4', html: 'List Item 4'}
    ]);
     * </code></pre></p>
     *
     * <p><b><u>Templating</u></b></p>
     * <p>The real power is in the built-in templating. Instead of creating or appending any elements,
     * <tt>{@link #createTemplate}</tt> returns a Template object which can be used over and over to
     * insert new elements. Revisiting the example above, we could utilize templating this time:
     * <pre><code>
    // create the node
    var list = dh.append('my-div', {tag: 'ul', cls: 'my-list'});
    // get template
    var tpl = dh.createTemplate({tag: 'li', id: 'item{0}', html: 'List Item {0}'});

    for(var i = 0; i < 5, i++){
        tpl.append(list, [i]); // use template to append to the actual node
    }
     * </code></pre></p>
     * <p>An example using a template:<pre><code>
    var html = '<a id="{0}" href="{1}" class="nav">{2}</a>';

    var tpl = new Ext.DomHelper.createTemplate(html);
    tpl.append('blog-roll', ['link1', 'http://www.jackslocum.com/', "Jack&#39;s Site"]);
    tpl.append('blog-roll', ['link2', 'http://www.dustindiaz.com/', "Dustin&#39;s Site"]);
     * </code></pre></p>
     *
     * <p>The same example using named parameters:<pre><code>
    var html = '<a id="{id}" href="{url}" class="nav">{text}</a>';

    var tpl = new Ext.DomHelper.createTemplate(html);
    tpl.append('blog-roll', {
        id: 'link1',
        url: 'http://www.jackslocum.com/',
        text: "Jack&#39;s Site"
    });
    tpl.append('blog-roll', {
        id: 'link2',
        url: 'http://www.dustindiaz.com/',
        text: "Dustin&#39;s Site"
    });
     * </code></pre></p>
     *
     * <p><b><u>Compiling Templates</u></b></p>
     * <p>Templates are applied using regular expressions. The performance is great, but if
     * you are adding a bunch of DOM elements using the same template, you can increase
     * performance even further by {@link Ext.Template#compile "compiling"} the template.
     * The way "{@link Ext.Template#compile compile()}" works is the template is parsed and
     * broken up at the different variable points and a dynamic function is created and eval'ed.
     * The generated function performs string concatenation of these parts and the passed
     * variables instead of using regular expressions.
     * <pre><code>
    var html = '<a id="{id}" href="{url}" class="nav">{text}</a>';

    var tpl = new Ext.DomHelper.createTemplate(html);
    tpl.compile();

    //... use template like normal
     * </code></pre></p>
     *
     * <p><b><u>Performance Boost</u></b></p>
     * <p>DomHelper will transparently create HTML fragments when it can. Using HTML fragments instead
     * of DOM can significantly boost performance.</p>
     * <p>Element creation specification parameters may also be strings. If {@link #useDom} is <tt>false</tt>,
     * then the string is used as innerHTML. If {@link #useDom} is <tt>true</tt>, a string specification
     * results in the creation of a text node. Usage:</p>
     * <pre><code>
    Ext.DomHelper.useDom = true; // force it to use DOM; reduces performance
     * </code></pre>
     * @singleton
     */
    Ext.DomHelper = function(){
        var tempTableEl = null,
            emptyTags = /^(?:br|frame|hr|img|input|link|meta|range|spacer|wbr|area|param|col)$/i,
            tableRe = /^table|tbody|tr|td$/i,
            confRe = /tag|children|cn|html$/i,
            tableElRe = /td|tr|tbody/i,
            cssRe = /([a-z0-9-]+)\s*:\s*([^;\s]+(?:\s*[^;\s]+)*);?/gi,
            endRe = /end/i,
            pub,
            // kill repeat to save bytes
            afterbegin = 'afterbegin',
            afterend = 'afterend',
            beforebegin = 'beforebegin',
            beforeend = 'beforeend',
            ts = '<table>',
            te = '</table>',
            tbs = ts+'<tbody>',
            tbe = '</tbody>'+te,
            trs = tbs + '<tr>',
            tre = '</tr>'+tbe;

        // private
        function doInsert(el, o, returnElement, pos, sibling, append){
            var newNode = pub.insertHtml(pos, Ext.getDom(el), createHtml(o));
            return returnElement ? Ext.get(newNode, true) : newNode;
        }

        // build as innerHTML where available
        function createHtml(o){
            var b = '',
                attr,
                val,
                key,
                cn;

            if(typeof o == "string"){
                b = o;
            } else if (Ext.isArray(o)) {
                for (var i=0; i < o.length; i++) {
                    if(o[i]) {
                        b += createHtml(o[i]);
                    }
                };
            } else {
                b += '<' + (o.tag = o.tag || 'div');
                for (attr in o) {
                    val = o[attr];
                    if(!confRe.test(attr)){
                        if (typeof val == "object") {
                            b += ' ' + attr + '="';
                            for (key in val) {
                                b += key + ':' + val[key] + ';';
                            };
                            b += '"';
                        }else{
                            b += ' ' + ({cls : 'class', htmlFor : 'for'}[attr] || attr) + '="' + val + '"';
                        }
                    }
                };
                // Now either just close the tag or try to add children and close the tag.
                if (emptyTags.test(o.tag)) {
                    b += '/>';
                } else {
                    b += '>';
                    if ((cn = o.children || o.cn)) {
                        b += createHtml(cn);
                    } else if(o.html){
                        b += o.html;
                    }
                    b += '</' + o.tag + '>';
                }
            }
            return b;
        }

        function ieTable(depth, s, h, e){
            tempTableEl.innerHTML = [s, h, e].join('');
            var i = -1,
                el = tempTableEl,
                ns;
            while(++i < depth){
                el = el.firstChild;
            }
    //      If the result is multiple siblings, then encapsulate them into one fragment.
            if(ns = el.nextSibling){
                var df = document.createDocumentFragment();
                while(el){
                    ns = el.nextSibling;
                    df.appendChild(el);
                    el = ns;
                }
                el = df;
            }
            return el;
        }

        /**
         * @ignore
         * Nasty code for IE's broken table implementation
         */
        function insertIntoTable(tag, where, el, html) {
            var node,
                before;

            tempTableEl = tempTableEl || document.createElement('div');

            if(tag == 'td' && (where == afterbegin || where == beforeend) ||
               !tableElRe.test(tag) && (where == beforebegin || where == afterend)) {
                return;
            }
            before = where == beforebegin ? el :
                     where == afterend ? el.nextSibling :
                     where == afterbegin ? el.firstChild : null;

            if (where == beforebegin || where == afterend) {
                el = el.parentNode;
            }

            if (tag == 'td' || (tag == 'tr' && (where == beforeend || where == afterbegin))) {
                node = ieTable(4, trs, html, tre);
            } else if ((tag == 'tbody' && (where == beforeend || where == afterbegin)) ||
                       (tag == 'tr' && (where == beforebegin || where == afterend))) {
                node = ieTable(3, tbs, html, tbe);
            } else {
                node = ieTable(2, ts, html, te);
            }
            el.insertBefore(node, before);
            return node;
        }

        /**
         * @ignore
         * Fix for IE9 createContextualFragment missing method
         */
        function createContextualFragment(html){
            var div = document.createElement("div"),
                fragment = document.createDocumentFragment(),
                i = 0,
                length, childNodes;

            div.innerHTML = html;
            childNodes = div.childNodes;
            length = childNodes.length;

            for (; i < length; i++) {
                fragment.appendChild(childNodes[i].cloneNode(true));
            }

            return fragment;
        }

        pub = {
            /**
             * Returns the markup for the passed Element(s) config.
             * @param {Object} o The DOM object spec (and children)
             * @return {String}
             */
            markup : function(o){
                return createHtml(o);
            },

            /**
             * Applies a style specification to an element.
             * @param {String/HTMLElement} el The element to apply styles to
             * @param {String/Object/Function} styles A style specification string e.g. 'width:100px', or object in the form {width:'100px'}, or
             * a function which returns such a specification.
             */
            applyStyles : function(el, styles){
                if (styles) {
                    var matches;

                    el = Ext.fly(el);
                    if (typeof styles == "function") {
                        styles = styles.call();
                    }
                    if (typeof styles == "string") {
                        /**
                         * Since we're using the g flag on the regex, we need to set the lastIndex.
                         * This automatically happens on some implementations, but not others, see:
                         * http://stackoverflow.com/questions/2645273/javascript-regular-expression-literal-persists-between-function-calls
                         * http://blog.stevenlevithan.com/archives/fixing-javascript-regexp
                         */
                        cssRe.lastIndex = 0;
                        while ((matches = cssRe.exec(styles))) {
                            el.setStyle(matches[1], matches[2]);
                        }
                    } else if (typeof styles == "object") {
                        el.setStyle(styles);
                    }
                }
            },
            /**
             * Inserts an HTML fragment into the DOM.
             * @param {String} where Where to insert the html in relation to el - beforeBegin, afterBegin, beforeEnd, afterEnd.
             * @param {HTMLElement} el The context element
             * @param {String} html The HTML fragment
             * @return {HTMLElement} The new node
             */
            insertHtml : function(where, el, html){
                var hash = {},
                    hashVal,
                    range,
                    rangeEl,
                    setStart,
                    frag,
                    rs;

                where = where.toLowerCase();
                // add these here because they are used in both branches of the condition.
                hash[beforebegin] = ['BeforeBegin', 'previousSibling'];
                hash[afterend] = ['AfterEnd', 'nextSibling'];

                if (el.insertAdjacentHTML) {
                    if(tableRe.test(el.tagName) && (rs = insertIntoTable(el.tagName.toLowerCase(), where, el, html))){
                        return rs;
                    }
                    // add these two to the hash.
                    hash[afterbegin] = ['AfterBegin', 'firstChild'];
                    hash[beforeend] = ['BeforeEnd', 'lastChild'];
                    if ((hashVal = hash[where])) {
                        el.insertAdjacentHTML(hashVal[0], html);
                        return el[hashVal[1]];
                    }
                } else {
                    range = el.ownerDocument.createRange();
                    setStart = 'setStart' + (endRe.test(where) ? 'After' : 'Before');
                    if (hash[where]) {
                        range[setStart](el);
                        if (!range.createContextualFragment) {
                            frag = createContextualFragment(html);
                        }
                        else {
                            frag = range.createContextualFragment(html);
                        }
                        el.parentNode.insertBefore(frag, where == beforebegin ? el : el.nextSibling);
                        return el[(where == beforebegin ? 'previous' : 'next') + 'Sibling'];
                    } else {
                        rangeEl = (where == afterbegin ? 'first' : 'last') + 'Child';
                        if (el.firstChild) {
                            range[setStart](el[rangeEl]);
                            if (!range.createContextualFragment) {
                                frag = createContextualFragment(html);
                            }
                            else {
                                frag = range.createContextualFragment(html);
                            }
                            if(where == afterbegin){
                                el.insertBefore(frag, el.firstChild);
                            }else{
                                el.appendChild(frag);
                            }
                        } else {
                            el.innerHTML = html;
                        }
                        return el[rangeEl];
                    }
                }
                throw 'Illegal insertion point -> "' + where + '"';
            },

            /**
             * Creates new DOM element(s) and inserts them before el.
             * @param {Mixed} el The context element
             * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
             * @param {Boolean} returnElement (optional) true to return a Ext.Element
             * @return {HTMLElement/Ext.Element} The new node
             */
            insertBefore : function(el, o, returnElement){
                return doInsert(el, o, returnElement, beforebegin);
            },

            /**
             * Creates new DOM element(s) and inserts them after el.
             * @param {Mixed} el The context element
             * @param {Object} o The DOM object spec (and children)
             * @param {Boolean} returnElement (optional) true to return a Ext.Element
             * @return {HTMLElement/Ext.Element} The new node
             */
            insertAfter : function(el, o, returnElement){
                return doInsert(el, o, returnElement, afterend, 'nextSibling');
            },

            /**
             * Creates new DOM element(s) and inserts them as the first child of el.
             * @param {Mixed} el The context element
             * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
             * @param {Boolean} returnElement (optional) true to return a Ext.Element
             * @return {HTMLElement/Ext.Element} The new node
             */
            insertFirst : function(el, o, returnElement){
                return doInsert(el, o, returnElement, afterbegin, 'firstChild');
            },

            /**
             * Creates new DOM element(s) and appends them to el.
             * @param {Mixed} el The context element
             * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
             * @param {Boolean} returnElement (optional) true to return a Ext.Element
             * @return {HTMLElement/Ext.Element} The new node
             */
            append : function(el, o, returnElement){
                return doInsert(el, o, returnElement, beforeend, '', true);
            },

            /**
             * Creates new DOM element(s) and overwrites the contents of el with them.
             * @param {Mixed} el The context element
             * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
             * @param {Boolean} returnElement (optional) true to return a Ext.Element
             * @return {HTMLElement/Ext.Element} The new node
             */
            overwrite : function(el, o, returnElement){
                el = Ext.getDom(el);
                el.innerHTML = createHtml(o);
                return returnElement ? Ext.get(el.firstChild) : el.firstChild;
            },

            createHtml : createHtml
        };
        return pub;
    }();