A: めっちゃ好き かっこよすぎ
A:あッ 来週ドラマ出るし 見ないとだよ
From the context (them talking about a celebrity), I understood that "見ないとだ" is similar to "見ないといけない". But when I searched for it online, an user on https://hinative.com/en-US/questions/240162 said that it isn't correct Japanese. Is that the case, and if so, how common is it?