Solving the Slight Render Delay in Applying New CSS Using React

Puzzled by a perplexing issue in your React application? Have you noticed a slight delay when applying conditional CSS styles? If you’re seeking answers and eager to enhance your understanding of React’s rendering process, you’re in the right place. In this comprehensive blog post, we’ll explore a real-world scenario involving a small React app, uncover the cause of the render delay, analyze the code responsible, and provide effective strategies to eliminate the delay. Let’s dive into the depths of React and shed light on this enigma!

Understanding the Issue: Picture this: You’re developing a small React app to familiarize yourself with the framework. Everything seems to be working smoothly until you notice a visible delay, lasting mere milliseconds, when applying conditional CSS using React. In particular, you observe a momentary inconsistency in the rendering of CSS styles after a state transition occurs.

Analyzing the Code: To investigate the issue, let’s examine the code snippet at the heart of the problem. We have a component called “Word” that renders a button. The button’s appearance is determined by the component’s state, and conditional CSS classes are applied accordingly.

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export default function Word({ word, state, onClick }) {
  return (
    <button
      id='word'
      disabled={state !== 'gameover'}
      onClick={onClick}
      className={state === 'timesup' ? 'timesup' : ''}
    >
      {state === 'playing' && word}
      {state === 'gameover' && 'GO'}
      {state === 'timesup' && 'Time\'s up!'}
    </button>
  )
}

In the main App.js component, the Word component is rendered with the provided props: word, state, and onClick. The application state is managed using React’s useState hook. A function, handleTimesUp, is responsible for transitioning the state from 'gameover' to 'timesup' and back to 'gameover' after a delay.

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const [state, setState] 







 = useState('gameover');

const handleTimesUp = async event => {
  setState('timesup');
  await sleep(3000);
  setState('gameover');
}

const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));

The CSS class 'timesup' is defined in an external CSS file, adding the styles of color: red and font-weight: bold to the button.

Understanding the Render Delay: Now, let’s unravel the mystery behind the render delay. When the state transition occurs inside the handleTimesUp function, a noticeable delay manifests between the moment the text changes to “Time’s up” and when the corresponding CSS styles are applied. During this brief period, the text is momentarily rendered with its previous color.

Understanding the Solution: To address this render delay and ensure consistent rendering of CSS styles, we can employ a couple of effective strategies:

1. Utilize the useEffect Hook: Wrap the logic responsible for applying CSS styles inside a useEffect hook. By doing so, we ensure that the styles are applied consistently after each render. Update your code as follows:

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export default function Word({ word, state, onClick }) {
  useEffect(() => {
    // Apply any necessary CSS adjustments here
  }, [state] 








);

  return (
    <button
      id='word'
      disabled={state !== 'gameover'}
      onClick={onClick}
      className={state === 'timesup' ? 'timesup' : ''}
    >
      {state === 'playing' && word