Add element before/after text selection

I'm looking for function which allows me to build some element before or after selected text. Something similar like this one javascript replace selection all browsers but for adding some content before or after selection instead of replacing it, like after() and before() jQuery methods. Should I use some DOM selection method, if yes which one? Or does exist something easier to carry it out?

Here's a pair of functions to do this.

Live example: http://jsfiddle.net/hjfVw/

Code:

var insertHtmlBeforeSelection, insertHtmlAfterSelection;

(function() {
    function createInserter(isBefore) {
        return function(html) {
            var sel, range, node;
            if (window.getSelection) {
                // IE9 and non-IE
                sel = window.getSelection();
                if (sel.getRangeAt && sel.rangeCount) {
                    range = window.getSelection().getRangeAt(0);
                    range.collapse(isBefore);

                    // Range.createContextualFragment() would be useful here but is
                    // non-standard and not supported in all browsers (IE9, for one)
                    var el = document.createElement("div");
                    el.innerHTML = html;
                    var frag = document.createDocumentFragment(), node, lastNode;
                    while ( (node = el.firstChild) ) {
                        lastNode = frag.appendChild(node);
                    }
                    range.insertNode(frag);
                }
            } else if (document.selection && document.selection.createRange) {
                // IE < 9
                range = document.selection.createRange();
                range.collapse(isBefore);
                range.pasteHTML(html);
            }
        }
    }

    insertHtmlBeforeSelection = createInserter(true);
    insertHtmlAfterSelection = createInserter(false);
})();