“When Not to Use useMemo, useCallback, and useReducer in React”

dani orooji — Sun, 07 Sep 2025 13:18:41 +0000

React gives us some amazing hooks like useCallback, useMemo, and useReducer. They’re powerful, but here’s the catch: using them in the wrong place can actually make your app slower and harder to maintain.
In this post, I’ll break down:

What each hook does
When you should use it
When you shouldn’t use it (common anti-patterns)
Better real-world examples

🔹 useCallback

✅ What it does
Keeps a function reference stable between renders. Useful when passing callbacks to memoized child components.

❌ When NOT to use it
On simple inline functions (onClick={() => setOpen(true)})
When you’re not passing the function to a child component
If the child isn’t wrapped in React.memo
✅ Good example

import { useCallback, useState, memo } from "react";

const Button = memo(({ onClick }) => {
  console.log("Button rendered");
  return <button onClick={onClick}>Click Me</button>;
});

export default function App() {
  const [count, setCount] = useState(0);

  // ✅ useCallback prevents function recreation on each render
  const handleClick = useCallback(() => {
    console.log("Clicked!");
  }, []);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
      <Button onClick={handleClick} />
    </div>
  );
}

Without useCallback, the would re-render every time count changes.
🔹 useMemo
✅ What it does
Memoizes the result of a calculation so it’s only recomputed when dependencies change.
❌ When NOT to use it

For cheap operations (a + b)
For small lists or trivial filtering/sorting
Just “because” (it adds overhead itself) ✅ Good example

import { useMemo, useState } from "react";

export default function App() {
  const [filter, setFilter] = useState("");
  const [items] = useState(
    Array.from({ length: 10000 }, (_, i) => `Item ${i + 1}`)
  );

  // ✅ Expensive filtering only runs when "filter" changes
  const filteredItems = useMemo(() => {
    console.log("Filtering...");
    return items.filter((item) => item.includes(filter));
  }, [filter, items]);

  return (
    <div>
      <input
        value={filter}
        onChange={(e) => setFilter(e.target.value)}
        placeholder="Search..."
      />
      <ul>
        {filteredItems.slice(0, 10).map((item) => (
          <li key={item}>{item}</li>
        ))}
      </ul>
    </div>
  );
}

If you filter a huge list without useMemo, React would recompute the filter on every keystroke, even if unrelated state changes.
🔹 useReducer
✅ What it does

Alternative to useState for managing complex state with multiple transitions.
❌ When NOT to use it

When state is simple (isOpen, count, inputValue)
When you don’t need multiple actions or a reducer function
For small components where useState is enough ✅ Good example

import { useReducer } from "react";

function reducer(state, action) {
  switch (action.type) {
    case "add":
      return { ...state, todos: [...state.todos, action.payload] };
    case "remove":
      return {
        ...state,
        todos: state.todos.filter((t, i) => i !== action.index),
      };
    default:
      return state;
  }
}

export default function App() {
  const [state, dispatch] = useReducer(reducer, { todos: [] });

  return (
    <div>
      <button onClick={() => dispatch({ type: "add", payload: "Learn Hooks" })}>
        Add Todo
      </button>
      <ul>
        {state.todos.map((todo, i) => (
          <li key={i}>
            {todo}{" "}
            <button onClick={() => dispatch({ type: "remove", index: i })}>
              ❌
            </button>
          </li>
        ))}
      </ul>
    </div>
  );
}

For complex state transitions like a todo list, shopping cart, or form wizard, useReducer shines. For a simple counter? useState is enough.
💡What about you? Have you ever overused these hooks and then realized they were unnecessary? Share your experience in the comments!

DEV Community: dani orooji

“When Not to Use useMemo, useCallback, and useReducer in React”