Como criar uma Preview URL Dinâmica com React e useMemo

Introduction

In this tutorial, you will learn how to create a dynamic preview URL in React using the useMemo hook. This technique optimizes performance by preventing unnecessary recalculations, ultimately enhancing user experience. You will implement a video preview feature that efficiently handles file uploads and displays a thumbnail.

Step 1: Understanding useMemo

• useMemo is a React hook that takes a function and an array of dependencies.
• It helps avoid recalculating a value on every render, which can improve performance significantly.
• Key usage:
  • The memoized value will only be recalculated when one of the dependencies changes.

Step 2: Setting Up the Video File State

• Initialize a state to hold the video file using the useState hook.
• Example code:

  const [videoFile, setVideoFile] = useState(null);
  

Step 3: Creating the Preview URL

• Use useMemo to generate the preview URL when the videoFile changes.
• Implement the following:

  const previewUrl = useMemo(() => {
    if (!videoFile) return null;
    return URL.createObjectURL(videoFile);
  }, [videoFile]);
  

Step 4: Implementing the Video Tag

• Create a video tag in your component to display the preview.
• Set the video controls to false to show only the thumbnail initially.
• Example code:

  return (
    <video src={previewUrl} controls={false} />
  );
  

Step 5: Handling Errors with Dependencies

• If you encounter issues like a missing module (e.g., 'twind CSS animate'), check your terminal.
• Use the following command to reinstall the module:

  npm install twind
  

Step 6: Preventing User Interaction

• To avoid user interaction with the video tag, set the CSS property pointer-events to none.
• Example CSS:

  video {
    pointer-events: none;
  }
  

Step 7: Adjusting Video Display

• Use CSS to ensure the video occupies the full area of its container.
• Apply the following styles:

  .video-container {
    position: relative;
  }
  
  video {
    position: absolute;
    inset: 0; /* This will stretch the video to fill the container */
  }
  

Step 8: Demonstrating Video Preview Functionality

• Implement a modal that can be reopened by clicking on the thumbnail.
• Ensure the modal displays the video using the previewUrl.

Conclusion

You have successfully created a dynamic preview URL for videos using React's useMemo hook. This tutorial covered setting up state, generating a preview URL, and adjusting video display properties. To further enhance your application, consider adding file type validation and improving the user interface. Experiment with these concepts to solidify your understanding and improve your projects.