To put it simply, before explaining this build, you have to understand tanky dps and gold items. League of Legends is about which team can more quickly arrive at its late game, which is more about creeps slain(cs), and total gold earned. Enter gold per 10 items. These items effectively double your passive gold earned. While this might not sound like a lot, if kept for long enough early game, these items will make a champion with 0 kills effectively have a champion kill for every 5 minutes they have 2 of these items. Given that the average length of a game is close to 30-40 minutes, assuming equal skill, that can be as much gold as 4-5 champion kills, while simply laning. How does this relate to tanky dps, you might ask yourself. Simple, tanky dps champions tend to benefit a large amount from these items because of their higher strength early game meaning you won't tend to get 0 kills, you'll get 2-3 kills, while not dying, assuming you play effectively, and will have, at 20 minutes, the gold equivalent of 5 champion kills, if you're having a bad game.

The idea of Jarvan IV is, I think, seriously misunderstood. Many people think of him as normal dps, or a normal tank. He is neither of these. While building minimal damage, he can deal rather large amounts a damage with martial cadence(10% of current enemy hp every 6 seconds), his knock up combo(demacian standard+dragon strike), and cataclysm hit all together very hard. However, when examining these abilities, Jarvan is intended to be the initiator of teamfights, not the real tank. He can quickly enter the fight, knocking up the beefy dps/tanks in front, and then cataclysm back to the enemy teams carries. From this range, and hemmed in as they are, most carries will choose to flash out, or lacking flash, die to the Exemplar of Demacia in close range. In either case, it creates 2 separate groups of enemies, 2-3 carries in back, 2-3 tanky people in front. Which means that the other 4 people on your team, have an easier time focusing down the isolated enemy champions, and pushing 4v2 or 5v2 is a lot easier than pushing 5v5. The emphasis of this build is to win games, and the only guaranteed way to win games is pushing the enemy nexus. To that end, a teamfight is a win if you can kill enough enemy champs to push towers, it doesn't have to be an ace, and a good Jarvan knows that. Pushing 4v2 or 5v2 can be a faster win than insisting on only pushing after an ace. The reason I say this is because Cataclysm facilitates this type of pushing over pushing post ace, but both are equally effective.

Jarvan's laning phase, solo or duo, is almost stupidly good. He has a knock up, an aoe slow, a terrain zone. These all together, mean that no matter who they have on the lane, you have more cc than them. Even if your partner has no cc, you will be able to out cc them. Especially if you run exhaust. Basically, farm until you hit six, making sure to harass with martial cadence, and at lvl 6, collect a double kill. I know that sounds over simplified, but if your lane partner has any damage what so ever, you will get at least one kill. The only other rules for laning are very simple. 1)Get philo stone, boots, and avarice blade early. More money and more move speed are at the core of this build. Eventually you will be able to push towers and pursue enemies better than almost any other champion, except maybe someone like Kassadin or Ezreal. 2) Get phage before you get brutalizer. Phage is hp/ad/slow vs. Brutalizers ad/armorpen/cdr. Simply put, with avarice blade and philo stone, it is better to have phage early because it gives you more ad and some much needed survivability. 3) Don't be afraid to use the Demacian Standard+Dragonstrike knock up to harass with your martial cadence really frequently once you have philo stone. With all this in mind, you will never lose a lane unless you are out ganked or have a poor lane partner for Jarvan, which consists only of other tanks.

More than any other time in a match, this is when Jarvan gets to shine. You have the ability to quickly engage and enemy team, leaving them in the air as you do it, and focus a carry as the rest of your team engages. With any other crowd control on your team, you will be able to quickly dispatch the enemies who were isolated by Cataclysm, with relatively low risk to your teammates. The other important part of this build, is understanding as a tanky-dps initiator, you can, and often will, die. That is fine. It is inefficient to focus Jarvan, and you want them to focus you. In fact, if you are the first target to die, and you aren't the most fed person on your team, it is entirely to your benefit. To put it simply, between your knock up, shield, and the inherent tankiness of this build, if the other team focuses you, and not your carries, you have achieved success. And even with you dead, they will have lost three enemies, and your team can collect a tower. In essence, with a good Jarvan initiated teamfight, you can always capitalize on an enemy tower, dragon, or Baron Nashor, should you desire. This makes Jarvan, in my opinion, on the tier of Amumu and Shen in terms of ability to game changingly initiate in teamfights. I have had teams losing games, used my Standard + Dragon Strike combo, and then Cataclysm, followed immediately by your shield, and you can, and usually will, win a teamfight.

When you jungle as Jarvan, you do your whole build differently. First and foremost, rush madred's razor and then boots, and finish wriggle's lantern. Then, ideally, build banshee's veil. After that, Jarvan should be built normally. Jarvan can and should start at blue when jungling, move to wolves, then ghosts, then red, and finish little golems. Doing this, you will hit lvl 4 in your first pass through the jungle, and then immediately gank mid or bottom lane. This will allow you to be able to dragon by lvl 7 with wriggles, and easily get your team ahead in both kills, and gold.

Pros
1.One of the best initiators in the game.
2.Good base dps on his abilites
3.One of the highest CC of any champ in LoL
4.Great ability to farm, combined with Gold/10 is amazing.
5.Good laning phase, but fantastic late game
6.Standard and Dragonstrike make Jarvan an incredibly fast jungler
7.Jarvan is hard to gank, especially while jungling

Cons
1.You will be focused, and dying sucks
2.Your knock up is fantastic, but has an annoyingly long cooldown
3.If the enemy team has a lot of cc, you can't initiate until you have banshee's veil
4.Without good team support, Jarvan is a useless champion, so he's better with premades
5.This build precludes the idea of dying early, if you do, you're done
6.Jungle Jarvan is more kill reliant than laning Jarvan