ReSharper дает & ldquo; @ & rdquo; префикс к имени переменной в лямбда-выражении

Вы можете поместить маркерный диапазон в конце выделения, получить его координаты с помощью jQuery, поместить свою кнопку в эти координаты и удалить маркерный диапазон.

Ниже вы должны начать:

var markSelection = (function() {
    var markerTextChar = "\ufeff";
    var markerTextCharEntity = "";

    var markerEl, markerId = "sel_" + new Date().getTime() + "_" + Math.random().toString().substr(2);

    var selectionEl;

    return function() {
        var sel, range;

        if (document.selection && document.selection.createRange) {
            // Clone the TextRange and collapse
            range = document.selection.createRange().duplicate();
            range.collapse(false);

            // Create the marker element containing a single invisible character by creating literal HTML and insert it
            range.pasteHTML('<span id="' + markerId + '" style="position: relative;">' + markerTextCharEntity + '</span>');
            markerEl = document.getElementById(markerId);
        } else if (window.getSelection) {
            sel = window.getSelection();

            if (sel.getRangeAt) {
                range = sel.getRangeAt(0).cloneRange();
            } else {
                // Older WebKit doesn't have getRangeAt
                range = document.createRange();
                range.setStart(sel.anchorNode, sel.anchorOffset);
                range.setEnd(sel.focusNode, sel.focusOffset);

                // Handle the case when the selection was selected backwards (from the end to the start in the
                // document)
                if (range.collapsed !== sel.isCollapsed) {
                    range.setStart(sel.focusNode, sel.focusOffset);
                    range.setEnd(sel.anchorNode, sel.anchorOffset);
                }
            }

            range.collapse(false);

            // Create the marker element containing a single invisible character using DOM methods and insert it
            markerEl = document.createElement("span");
            markerEl.id = markerId;
            markerEl.appendChild( document.createTextNode(markerTextChar) );
            range.insertNode(markerEl);
        }

        if (markerEl) {
            // Lazily create element to be placed next to the selection
            if (!selectionEl) {
                selectionEl = document.createElement("div");
                selectionEl.style.border = "solid darkblue 1px";
                selectionEl.style.backgroundColor = "lightgoldenrodyellow";
                selectionEl.innerHTML = "&lt;- selection";
                selectionEl.style.position = "absolute";

                document.body.appendChild(selectionEl);
            }

            // Find markerEl position http://www.quirksmode.org/js/findpos.html
        var obj = markerEl;
        var left = 0, top = 0;
        do {
            left += obj.offsetLeft;
            top += obj.offsetTop;
        } while (obj = obj.offsetParent);

            // Move the button into place.
            // Substitute your jQuery stuff in here
            selectionEl.style.left = left + "px";
            selectionEl.style.top = top + "px";

            markerEl.parentNode.removeChild(markerEl);
        }
    };
})();