どこか details

※

somewhere — どこ plus か, a place the speaker cannot or need not name + go

dokokani iku

somewhere — どこ plus か, a place the speaker cannot or need not name

meaning: go somewhere

週末しゅうまつはどこかに出かけるでかけるつもりです。

shuumatsu wa dokokani dekakeru tsumori desu.

I'm planning to go out somewhere this weekend. neutral

今度こんどの休やすみ、どっか行いこうよ。

kondo no yasumi, dokka ikou yo.

Let's go somewhere on the next day off. casual

Examples

somewhere — the place is left open, either because the speaker does not know it or because any one will do

週末しゅうまつはどこかに出でかけるつもりです。

shuumatsu wa dokokanidekakeru tsumori desu.

I'm planning to go out somewhere this weekend. neutral

今度こんどの休やすみ、どっか行いこうよ。

kondo no yasumi, dokka ikou yo.

Let's go somewhere on the next day off. casual

鍵かぎをどこかに置おき忘わすれてしまったみたいです。

kagi o dokoka ni okiwasurete shimatta mitai desu.

It seems I've left my keys somewhere. neutral

どこかでお会あいしたことはありませんか。

dokoka de o ai shita koto wa arimasen ka.

Haven't we met somewhere before? formal

よろしければ、どこかで少すこしお休やすみになりませんか。

yoroshikereba, dokoka de sukoshi o yasumi ni narimasen ka.

If you'd like, won't you rest somewhere for a little while? formal

The same か leaves any question word open — 何なにか, 誰だれか, いつか,
どれか — and each keeps the particle its verb wants (誰だれかに聞きく).

とか
Both duck a specific answer, but とか is casual speech and gets there by naming a sample member (カフェとかで会あおう), while どこか names no member at all and stays register-neutral, so it is what a formal request uses (どこかで少々しょうしょうお待まちいただけますか).

どこにも〜ない
Same どこ, and the particle after it flips the sentence — か opens ONE unnamed place, も sweeps every place and demands a negative (どこにも置おいてない); どこか survives a negative only outside its scope (どこかに行いかないと), so the plain negation of どこかに行いった is どこにも行いかなかった.
か
Both are the particle か and the two co-occur freely (どこか行いきましたか) — the sentence-final one asks about the whole clause, this one only refuses to name the place, and in casual speech the asking half is carried by intonation alone (どこか行いった？).