获取/使用HTML文本区域内的选定位置

Question

   <textarea id="editor"></textarea>
   <input type="button" value="Insert Comment" onclick="document.getElementById('editor').value+='<'+'!--    -->\n'"/>

The program I created (summed up to the basics above) works as intended, however I was wondering if I could improve it. There is a textarea where you can type things, and upon clicking the input button it adds an HTML comment string to the text inside the textarea. I want it to add the < ! -- --> to the part of the textarea that was is selected (as in the place where text would show up next if you typed). Is that possible in raw Javascript preferably, or is there a library that would allow this to be possible?

Answer 1

Finding the cursor position in a text area is a fairly commonly asked question; inserting just less so. Take a look at these. There's some redundancy between them, but the discussion might be useful (or one might explain it better for you).

Insert text into textarea at cursor position (Javascript)

How do you get the cursor position in a textarea?

How do you get the cursor position in a textarea?