How to use value from modal tinymce windowManager?
If I read your question correctly, this is more related to Javascript programming than WordPress. To get the selected option value or text of a HTML select tag, use: var e = document.getElementById(“programming-language-id”); var value = e.options[e.selectedIndex].value; //your code doesn’t set option value var text = e.options[e.selectedIndex].text; //this will get the selected option text