This is more for informing the website, the gen 1 move-set chart for Jolteon is wrong.

Question

Jolteon learns double kick at level 30 not 42 and it doesn't learn thundershock at level 31.

EDIT: I've been reading up on it and i was partially wrong see i'm currently playing yellow, "gen 1" and waiting on lvl 31 for an electric attack since Jolteon has weak att but descent sp.att. the website chart is right for red/blue "gen 1" but not for yellow. So i'll end it with this if your playing yellow i'd suggest not wasting your Evee evolving it to Jolteon.

Comments

When did you evolve eevee? You get Thunder shock at level 16.
If you evolved eevee after level 16 you can't get thundershock anymore since eevee
can't learn it on level 16 .so to get an electric type move you need to evolve eevee
before or on level 16.But you can get Thunder on level 52

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Well on yellow you get your Evee at level 25 in Celadon so you can't evolve it early, so jolteon is pretty much useless till level 52 or if you saved the thunderbolt tm you get from Lt. Surge but like me i'm sure most people used it on their pikachu. So unless you can get lower level evee some how you have to raise a weak pokemon 27 level before you get any use out of Jolteon.

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I didn't play yellow so I didn't know

Answer 1

There are tabs for Red/Blue and Yellow on the movepool pages for each Pokemon.
The movepool page has the levels where you learn Double Kick and Thundershock as the correct levels.

Comments

yeah i figured that out afterward never saw the yellow tab for some reason probly bc most of them are the same for yellow. My mistake my vision not what it youst to be.