いいじゃん

that's good

→ 良い
phrase Uncommon #17,738
that's good Informal and often used to approve of something or reassure someone. With 〜ばいいじゃん, it suggests what someone should do, like “why don't you…?”
JA: そのシャツ、いいじゃん。
EN: That shirt looks good.

いいじゃんいいじゃん→

Nice, nice.

— 映画 聲の形 (2016)

ねえ亜紀もさちょっとは入れたらいいじゃん

Hey, Aki, why don’t you chip in a little too?

— 万引き家族 (2018)

別にいいじゃんかよ。

It's not like there's anything wrong with it.

お前のネクタイ、いいじゃん。

I like your tie.

お前の成績は俺よりいいじゃん。

Your grades are better than mine.

カバーでいいじゃん

A cover works just fine.

— Cosmic Princess Kaguya! (2026)

いいじゃん

That’s great!

— グッバイ、レーニン! (2003)

泣きたいなら思いっきり泣けばいいじゃん。

If you want to cry, then just cry your heart out.

眠いなら寝ればいいじゃん。

If you're sleepy, why don't you just go to sleep?