General Synonyms:
* Happily
* Gladly
* Delightedly
* Cheerfully
* With joy
* With pleasure
* With enthusiasm
* With gusto
* Exuberantly
* With abandon
More Specific Synonyms:
* Ebulliently: Expressing great enthusiasm and excitement.
* Exultantly: Feeling or expressing great happiness.
* Blissfully: Experiencing or showing perfect happiness.
* Rapturously: Feeling or expressing great joy or delight.
* Triumphantly: Feeling or expressing great victory or success.
The best synonym for "joyfully" will depend on the specific situation and the emotion you are trying to convey.