also: じゃじゃん
interjection
ta-dah!; voilà
Onomatopoeic interjection used when presenting something with a flourish, like revealing a surprise or showing off an accomplishment.
じゃじゃーん！見て、新しく買ったカメラだよ。
Ta-dah! Look, it's the new camera I bought.
ケーキができたよ。じゃじゃーん！
The cake is ready. Ta-dah!