Fix incorrect condition in "Chains of computations" example

[PaulyBearCoding]

Fixes #8097

Problem

In the "Chains of computations" section, the refactored example uses an incorrect condition that changes the game logic from the original:

// Current (incorrect)
if (goldCardCount <= 3) {
  setGoldCardCount(goldCardCount + 1);
} else {
  // advance round
}

This allows 5 gold cards before advancing the round, which differs from the original Effect-based example that advances after 4 gold cards.

Solution

Changed the condition from <= to <:

// Fixed
if (goldCardCount < 3) {
  setGoldCardCount(goldCardCount + 1);
} else {
  // advance round
}

Why This Fix is Correct

The original "bad" example increments first, then checks:

useEffect(() => {
  setGoldCardCount(c => c + 1);  // 0→1, 1→2, 2→3, 3→4
}, [card]);

useEffect(() => {
  if (goldCardCount > 3) {  // Triggers when count reaches 4
    setRound(r => r + 1);
    setGoldCardCount(0);
  }
}, [goldCardCount]);

This advances after 4 cards (when count reaches 4).

The fixed example checks before incrementing:

• With <= 3: Allows counts 0,1,2,3 to increment → 4 values → advances on 5th card ❌
• With < 3: Allows counts 0,1,2 to increment → 3 values → advances on 4th card ✅

Testing

Verified the fix by:

1. Tracing execution logic step-by-step
2. Building the docs site locally and confirming correct rendering
3. Checking that only the intended line was modified

Changes

• File: src/content/learn/you-might-not-need-an-effect.md
• Line: 440
• Change: goldCardCount <= 3 → goldCardCount < 3

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[github-actions]

Size changes

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[rickhanlonii]

I don't see the 5th card:

if (nextCard.gold) {
  if (goldCardCount <= 3) {
    // doesn't enter if there are 4 cards
    setGoldCardCount(goldCardCount + 1);
  } else {
    // ends at only 4 cards
    setGoldCardCount(0);
    setRound(round + 1);
    if (round === 5) {
      alert('Good game!');
    }
  }
}

[piowin]

I don't see the 5th card:

if (nextCard.gold) {
  if (goldCardCount <= 3) {
    // doesn't enter if there are 4 cards
    setGoldCardCount(goldCardCount + 1);
  } else {
    // ends at only 4 cards
    setGoldCardCount(0);
    setRound(round + 1);
    if (round === 5) {
      alert('Good game!');
    }
  }
}

@rickhanlonii, the fact that the program doesn't enter the first block when goldCardCount is equal to 4 doesn't mean that picking a gold card four times advances the game to the next round in this case - that is the issue. When goldCardCount is equal to 3, setGoldCardCount(3+1) is executed which advances goldCardCount to 4, but doesn't advances round, therefore the user has to pick a fifth gold card so the else block is finally executed and setRound(round + 1) is called.

1. goldCardCount is equal to 0
2. the user picks a gold card (first time)
3. setGoldCardCount(0 + 1) is executed and then goldCardCount is equal to 1
4. the user picks a gold card (second time)
5. setGoldCardCount(1 + 1) is executed and then goldCardCount is equal to 2
6. the user picks a gold card (third time)
7. setGoldCardCount(2 + 1) is executed and then goldCardCount is equal to 3
8. the user picks a gold card (fourth time)
9. setGoldCardCount(3 + 1) is executed and then goldCardCount is equal to 4
10. the user picks a gold card (fifth time)
11. the else block is now executed as goldCardCount <= 3 is finally false
12. setGoldCardCount(0) and setRound(round + 1) are executed

[rickhanlonii]

I see, so it takes 5 clicks with a gold card next.

I was wrong, I confirmed your right in this sandbox:
https://codesandbox.io/p/devbox/amazing-star-mlmv44?utm_source=dotnew

[rickhanlonii]

Nice catch, thanks for helping me understand it