Basic example

jsPanel.create({
    content:     '<textarea id="simplemde"></textarea>',
    contentSize: '650 400',
    headerTitle: 'jsPanel with SimpleMDE',
    theme:       'primary',
    position:    'center-top 0 70',
    callback: function (panel) {
        var simplemde = new SimpleMDE({
            element: document.getElementById('simplemde')
        });
        $('.CodeMirror-wrap', panel.content).css({height: 'calc(100% - 83px)'});
        $('.CodeMirror', panel.content).css({minHeight: 0});
        $('#btn-1').attr('disabled', 'disabled');
    },
    onclosed: function () {
        $('#btn-1').attr('disabled', false);
    }
});