Add Link to Contenteditable

HTML

<input type="image" id="link" title="Insert Link" class="icon-bar-icon" src="https://image.flaticon.com/icons/svg/34/34735.svg" style="width:50px;height:50px;">
<input type="text" id="url" size="30" placeholder="https://">
<input type="button" id="linkBtn" value="Link">
<div id="editor" contenteditable="true" style="border:solid 1px;"></div>

JavaScript

function getCaretCharacterOffsetWithin(element) {
    var caretOffset = 0;
    var doc = element.ownerDocument || element.document;
    var win = doc.defaultView || doc.parentWindow;
    var sel;
    if (typeof win.getSelection != "undefined") {
        sel = win.getSelection();
        if (sel.rangeCount > 0) {
            var range = win.getSelection().getRangeAt(0);
            var preCaretRange = range.cloneRange();
            preCaretRange.selectNodeContents(element);
            preCaretRange.setEnd(range.endContainer, range.endOffset);
            caretOffset = preCaretRange.toString().length;
        }
    } else if ( (sel = doc.selection) && sel.type != "Control") {
        var textRange = sel.createRange();
        var preCaretTextRange = doc.body.createTextRange();
        preCaretTextRange.moveToElementText(element);
        preCaretTextRange.setEndPoint("EndToEnd", textRange);
        caretOffset = preCaretTextRange.text.length;
    }
    return caretOffset;
}

var update = function() {
  console.log(getCaretCharacterOffsetWithin(this));
};
$('#editor').on("mousedown mouseup keydown keyup", update);

$('#link').click(function(e) {
  e.preventDefault();
  setTimeout(function() {
    $('#url').focus();
  }, 100);
});

$('#linkBtn').click(function(e) {
  e.preventDefault();
  createLink();
});

function saveSelection() {
    if (window.getSelection) {
        sel = window.getSelection();
        if (sel.getRangeAt && sel.rangeCount) {
            var ranges = [];
            for (var i = 0, len = sel.rangeCount; i < len; ++i) {
                ranges.push(sel.getRangeAt(i));
            }
            return ranges;
        }
    } else if (document.selection && document.selection.createRange) {
        return document.selection.createRange();
    }
    return null;
}

function restoreSelection(savedSel) {
    if (savedSel) {
        if (window.getSelection) {
            sel = window.getSelection();
            sel.removeAllRanges();
            for...