This behavior is intentional and stems from React's Strict Mode, which is designed to help identify potential issues in your application.
Understanding the Behavior:
React's Strict Mode intentionally double-invokes certain lifecycle methods and hooks, including useEffect, during development. This practice aims to help developers identify side effects that might not be properly managed, such as those that should be cleaned up but aren't. By simulating the mounting and unmounting of components, React ensures that effects are resilient and that components can handle being mounted and unmounted multiple times without adverse effects.
Key Points:
Development Only: This double invocation occurs only in development mode when Strict Mode is enabled. In production builds, useEffect runs as expected, without the additional invocation.
Purpose: The goal is to help developers detect side effects that might not be properly cleaned up, ensuring that components are robust and free from memory leaks or unintended behaviors.
No Immediate Action Required: In most cases, this behavior doesn't necessitate changes to your code. However, it's essential to ensure that your effects are idempotent and properly handle setup and cleanup to prevent unintended consequences.
