やった

from the past tense of やる, literally meaning “I did it”, “you did it”, or “he/she did it”, the subject being implied in a context. In the case of interjection it always means “I did it”.

やった (rōmaji yatta)

1. hurrah! yay! I made it! (an interjection expressing approval, appreciation, or happiness.)
   • 1927, Denji Kuroshima, 雪のシベリア:

     戦闘の時と同じような銃声がしたかと思うと、兎は一間ほどの高さに、空に弧を描いて向うへとんだ。たしかに手ごたえがあった。
     「やった！　やった！」
     吉田は、銃をさげ、うしろの小村に一寸目くばせして、前へ馳せて行った。

     As soon as we heard a gunshot that matched that of a battle, the rabbit jumped to a height of 1 ken, drawing a curve in the air. It was a telling shot.
     "Hurray! Hurray!"
     With his gun slung off, and with a glance to Komura standing behind, Yoshida bolted off forward.

   • 2001 April 4, はっぱ隊 (music), “YATTA!”:

     お水 (みず)飲 (の)んだらうめー！（やったー！）
     日 (ひ)に当 (あ)たったらあったけー！（やったー！）
     腹 (はら)から笑 (わら)ったらおもしれー！（やったーやったー！）
     犬飼 (いぬかい)ってみたらかわいー！（やったー！）

     O-mizu nonda raumē! (yattaー!)
     Hi ni atattara attakē! (yattaー!)
     Hara kara warattara omoshirē! (yattaーyattaー!)
     Inu kaitte mitara kawaī! (yattaー!)

     When I drank the water, it tasted great! (Hurray!)
     When the sunlight hits me, it's warm! (Hurray!)
     When I laughed from my stomach, it's fun! (Hurray hurray!)
     When I got a dog, it was cute! (Hurray!)

やった (rōmaji yatta)

1. past tense of やる