Yandex Speller

(function ($) {
    CKEDITOR.replaceAll('ckeditor');
    CKEDITOR.on('instanceReady', function(ev) {
        let editor = ev.editor;
        if (!editor.spellCheckInited) {
            let editorBottomSelector = '.cke_inner';
            let editorBottom = $(editorBottomSelector);
            let spellCheckBar = $('
').addClass('spell-check-bar');
            editorBottom.append(spellCheckBar);
            editor.spellCheckBar = spellCheckBar;
            editor.spellCheckInited = true;
        }

        function clearSuggestions() {
            let suggestions = editor.spellCheckBar.find('.suggestion');

            if (suggestions.length) {
                suggestions.each(function(num, el) {
                    $(el).remove();
                });
            }
        }

function newSuggestion(wrong, fix, text) {

            let newSugg = $('');
            newSugg.addClass('suggestion');
            newSugg.text(wrong + ' ~> ' + fix);

            $(newSugg).on('click', function(ev) {
                text.data = text.data.replace(wrong, fix);
                $(ev.target).remove();
            });

            return newSugg;
        }

        function updateSuggestions(data, focusNode) {

            clearSuggestions();

            if (data.length) {
                data.forEach(function(item) {
                    if (item.s.length) {
                        let newSugg = newSuggestion(item.word, item.s[0], focusNode);
                        $(editor.spellCheckBar).append(newSugg);
                    }
                });
            }
        }

        function spellCheck() {
            let sel = editor.getSelection();
            if (!sel) { return; }
            let nativeSel = sel._.cache.nativeSel || null;
            if (!nativeSel) { return; }
            let focusNode = nativeSel.focusNode;
            if (!focusNode) { return; }
            let text = focusNode.data;
            if (!text) { return; }
            $.get('https://speller.yandex.net/services/spellservice.json/checkText?text=' + text, function(data) {
                updateSuggestions(data, focusNode)
            });
        }

        editor.document.on('mouseup', spellCheck);
        editor.on('change', spellCheck);
    });
})(jQuery);

.cke .spell-check-bar {
  display: block;
  padding: 0.5em;
}

.cke .spell-check-bar .suggestion {
  cursor: pointer;
  color: red;
  background: rgba(250,0,0,0.1);
  padding: 0.25em 0.5em;
  margin-left: 0;
  margin-top: 0;
  margin-right: 0.5em;
  margin-bottom: 0.5em;
  line-height: 1em;
  display: inline-block;
}

.cke .spell-check-bar .suggestion:hover {
  color: orange;
}