Q267- What happens when we omit the Dependency array from useEffect in React?

If you write:

useEffect(() => {
  console.log("Effect runs");
});

and omit the dependency array, React will run this effect after every single render.

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✅ 1. Effect runs after every render (initial + re-renders)

That means:

• Runs after the first render
• Runs after every state update
• Runs after every prop change
• Runs after every parent re-render

This can easily cause:

• Performance issues
• Infinite loops
• Repeated API calls

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❗ Example: Infinite Loop Scenario

useEffect(() => {
  setCount(count + 1);
});

🔥 This triggers:

• setCount() → re-render
• Effect runs again → another setCount()
• Loop continues forever ❌

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✅ 2. With dependency array omitted → same as writing:

useEffect(() => {
  // effect
}, undefined);

React treats it as: ➡️ Run on every render (default behavior)

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🔥 Summary of all useEffect variations

1️⃣ No dependency array

useEffect(() => {});

✔ Runs after every render
❌ Can easily cause infinite loops

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2️⃣ Empty dependency array

useEffect(() => {}, []);

✔ Runs only once (componentDidMount)

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3️⃣ With dependencies

useEffect(() => {}, [state, props]);

✔ Runs only when the values inside the array change

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🎯 Short Interview Answer

If you omit the dependency array, useEffect runs after every render. This includes the initial render and all subsequent re-renders, which can cause performance issues or infinite loops if the effect updates state.