BTW, I'm not sure why it says adding syntax highlighting to a <textarea> is impossible -- as the linked post says, you can turn the text invisible and add styled text in a separate div at the same position.
(author) Because then you're not adding syntax highlighting to the textarea, but to the div... I've done this before and it's janky, with many edge cases that require extra css fiddling. It's just not great. I would rather use a library like codemirror even in seemingly simple cases like that, but fortunately I don't have to anymore : - )
