Use Effect vs Component Body

TODO: collapasable, copyable, download, etc

In React, Each time a component is rendered, I want some logic to run. Should I put it in useEffect and not give it a dependency array?In React, if you want some logic to run every time a component is rendered, placing it directly in the component body, outside of any useEffect, useCallback, or other hooks that depend on specific dependencies, is the straightforward way to achieve this. Here’s a brief rundown on how and where to place your logic:

Placing Logic in the Component Body

If the logic you want to run does not involve side effects (e.g., updating state, fetching data, modifying the DOM directly), you can place it directly in the body of your function component. This code will run on every render:

function MyComponent() {
  // This will run on every render
  console.log('Component rendered');

  return <div>Hello, world!</div>;
}

Using useEffect Without Dependencies

If the logic includes side effects, you should use the useEffect hook. Placing it without any dependencies means it will run after every render, but it's important to note that it executes after the paint, so it doesn't block the browser painting process:

import { useEffect } from 'react';

function MyComponent() {
  useEffect(() => {
    // This will run after every render
    console.log('Component rendered with side effects');
  });  // No dependencies passed, runs on every render

  return <div>Hello, world!</div>;
}

Considerations

1. Performance: Running code on every render might lead to performance issues, especially if the code is heavy or if it modifies the state, causing additional renders.
2. Side Effects: If you're handling side effects, always use useEffect. Directly manipulating states or performing actions like data fetching without useEffect can lead to bugs and inconsistent states.
3. Dependencies: If your effect only needs to run when specific props or state values change, use the dependency array in useEffect to specify those values.

By considering the nature of your logic (whether it's a side effect or just computation), you can choose between placing it directly in the component body or inside a useEffect hook.

Use Effect vs Component Body created at Tue Jan 20 1970 20:07:53 GMT+0000 (Coordinated Universal Time)