How to get Gmail edit area with JavaScript

I need开发者_如何学JAVA to get the textarea used by Gmail for composing an email (is it a textarea at all?). How can I do this?

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In the Basic HTML version the textarea is:

<textarea name=body title="Message Body" rows=15 cols=50 wrap=virtual class=mi>

In the full version it's a Google custom editor, and not a textarea.