Why Does useState() Trigger Double Renders in React\'s Development Mode?

Why Does useState() Cause Double Renders in Development Mode?

In React, using useState for state management may trigger two renders during state updates. This behavior is attributed to React's Strict Mode, which enhances development debugging by simulating potential side effects.

Consider the following code snippet:

import React, { useState } from "react";
...
const [number, setNumber] = useState(0);
...
function changeNumber() {
    setNumber(state => state + 1);
}
...

When clicking the button that triggers the changeNumber function, you may observe two console logs signaling component re-renders. This is due to Strict Mode, which forces functions like useState updaters to execute twice in development environments.

React's documentation explains that Strict Mode detects and highlights potential side effects by intentionally re-invoking certain functions, including state updater functions like those passed to useState. The goal is to facilitate debugging and ensure deterministic behavior.

To mitigate this double rendering, you can disable Strict Mode by removing the following code from the entry point of your application:

ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  rootElement
);

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