React Answers

How to fix useEffect() is called twice even if an empty array is used as an argument with React?

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If useEffect is being called twice even when we pass an empty array [] as the second argument, it typically indicates that there’s a side effect that’s causing the component to re-render.

Here are a few potential reasons and solutions:

Dependency Array Mismatch

Ensure that the dependency array ([]) is correctly passed as the second argument to useEffect. Double-check that we are not accidentally providing a non-empty array, which would cause useEffect to run whenever any of those dependencies change.

Check Component Render Triggers

Review the component code to see if there are any state updates, prop changes, or other side effects triggering a re-render. Make sure that there are no unintentional side effects updating state or props inside the component.

Check for React Strict Mode

If we are using React Strict Mode (<React.StrictMode>), it can cause double rendering of certain lifecycle methods and hooks for performance debugging purposes. Make sure that we are not seeing this behavior due to Strict Mode.

Check for Higher Order Components (HOCs) or Wrapper Components**:

If our component is wrapped with HOCs or nested within wrapper components, they might be causing additional renders.

Check for Nested Components

If the component is part of a larger component tree, ensure that parent components aren’t causing additional renders that could affect our component.

Check for Context or Global State Changes

If our component relies on context or global state changes, ensure that those changes aren’t triggering re-renders.

Check for Custom Hooks or External Libraries

If we are using custom hooks or external libraries, review their implementation to ensure they’re not causing additional renders.

By carefully reviewing our component code and considering these potential causes, we should be able to identify and resolve the issue causing useEffect to be called twice.

By John Au-Yeung

Web developer specializing in React, Vue, and front end development.

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