Ckeditor - Load dynamic field values in "select" field

I am trying to load dynamic input values for a drop down field in ckeditor:

As you can see below when pressing the button no values are loaded in the drop-down:

I would like to have loaded the following values in my drop-down(which should be matched by the reged in the onLoad function):

As the snippet does not run on stack-snippets I put a fully working replication of the problem on codepen. See the following link: https://codepen.io/anon/pen/NBXObP

My plugin code looks like the following:

var selectedList = []

CKEDITOR.replace("editor", {
  extraPlugins: "insertData"
});

CKEDITOR.plugins.add( 'insertData', {

    icons: '',
    init: function( editor ) {

        editor.addCommand( 'insertData', new CKEDITOR.dialogCommand( 'insertDataDialog' ) );
        editor.ui.addButton( 'InsertData', {
            label: 'Insert InsertData',
            command: 'insertData',
            toolbar: 'insert'
        });

        if ( editor.contextMenu ) {
            editor.addMenuGroup( 'insertDataGroup' );
            editor.addMenuItem( 'insertDataItem', {
                label: 'Edit InsertData',
                icon: this.path + 'icons/insertData.png',
                command: 'insertData',
                group: 'insertDataGroup'
            });

            editor.contextMenu.addListener( function( element ) {
                if ( element.getAscendant( 'insertData', true ) ) {
                    return { insertDataItem: CKEDITOR.TRISTATE_OFF };
                }
            });
        }

        CKEDITOR.dialog.add( 'insertDataDialog', function (editor) {
    return {

        // Basic properties of the dialog window: title, minimum size.
        title: 'InsertData Properties',
        minWidth: 400,
        minHeight: 200,

        // Dialog window content definition.
        contents: [{
                // Definition of the Basic Settings dialog tab (page).
                id: 'tab-basic',
                label: 'Basic Settings',

                // The tab content.
                elements: [{
                        // Text input field for the insertData text.
                        type: 'select',
                        id: 'insertData',
                        label: 'Element',
                        items: selectedList,
                        'default': '',

                        onLoad: function (widget) {
                            var text = CKEDITOR.instances.editor.getData();
                            var selectedList = text.match(//g)
                            console.log("text: " + text)
                            console.log("selectedList: " + selectedList)
                        },

                        onChange: function (api) {
                            alert('Current value: ' + this.getValue());
                        }
                    },
                    {
                        type: 'text',
                        id: 'title',
                        label: 'InsertDatas',
                        validate: CKEDITOR.dialog.validate.notEmpty("InsertDatas field cannot be empty."),

                        setup: function (element) {
                            this.setValue(element.getAttribute("title"));
                        },

                        commit: function (element) {
                            element.setAttribute("title", this.getValue());
                        }
                    }

                ]
            },
        ],

        onShow: function () {

            var selection = editor.getSelection();
            var element = selection.getStartElement();

            if (element)
                element = element.getAscendant('insertData', true);

            if (!element || element.getName() != 'insertData') {
                element = editor.document.createElement('insertData');

                this.insertMode = true;
            } else
                this.insertMode = false;

            this.element = element;
                this.setupContent(this.element);
        },

        onOk: function () {
            var insertData = this.element;

            this.commitContent(insertData);
            if (this.insertMode)
                editor.insertElement(insertData);
        }
    };
});
    }
});

Why doesn`t the fields NOT load in the drop-down?

I appreciate your replies!

from Ckeditor - Load dynamic field values in "select" field