trying to set the data value of submit button

trying to set the data value of submit button

I've been having problems trying to set the data value of an elment. I
have the following:
<textarea class='pairing-comment' ></textarea>
<input data-comment="" data-global-id="187"
type="submit" id="pairing-comment-submit">
I'd like to update the the data-comment value when the user changes the
textarea (testing has shown this to be the only reliable way to get this
done):
$('textarea.pairing-comment').on('keyup',function() {
var com = $(this).val();
console.log("here i am in pairing-comment " + com); // works fine
$('#pairing-comment-submit').
data('comment', com); // not writing to the data-comment elment
});
What would be the jquery syntax to write what I want to the data-comment
value?
thx