Replay AI for Converting Legacy App UI to Modern React Code

TL;DR: Replay AI bridges the gap between outdated legacy application UIs and modern React code by analyzing video recordings of user interactions and reconstructing functional, maintainable components.

The biggest lie in software development is that rewriting legacy code is always the answer. Often, it's the only answer presented. But what if you could breathe new life into your crusty old UI without a complete rewrite? What if you could learn from its existing user flows instead of dismissing them?

The problem isn't necessarily the functionality of your legacy app. It's the outdated UI, the brittle codebase, the lack of maintainability. But users know how to use it. They've adapted to its quirks. Throwing all that institutional knowledge away is a massive waste.

That's where Replay AI comes in.

Reclaiming Legacy UI with Behavior-Driven Reconstruction#

Forget screenshot-to-code tools that merely replicate visual elements. Replay analyzes video recordings of users interacting with your legacy application. This "Behavior-Driven Reconstruction" approach is the key to unlocking true modernization. Replay understands what users are trying to do, not just what they see. It leverages Gemini to intelligently reconstruct functional UI components in modern React, preserving the core user flows while upgrading the underlying technology.

Why Video is the Secret Weapon#

Screenshots are static. They capture a moment in time. Video captures behavior. Replay uses this behavioral data to:

• •Infer User Intent: Understand the sequence of actions a user takes to achieve a specific goal.
• •Reconstruct Complex Interactions: Handle multi-step forms, dynamic content updates, and intricate navigation patterns.
• •Generate Realistic State Management: Accurately represent the application's state based on user actions.

This allows Replay to generate code that isn't just visually similar to the original, but also functionally equivalent and maintainable.

Replay AI in Action: A Practical Example#

Let's say you have a clunky, outdated Java Swing application with a complex data entry form. Users are familiar with the form's layout and workflow, but the underlying technology is a nightmare to maintain.

Here's how you can use Replay to modernize this UI:

Step 1: Record User Interactions#

Record a video of a user completing a typical data entry task in the legacy application. Ensure the video clearly captures all user actions, including mouse clicks, keyboard input, and form submissions.

Step 2: Upload to Replay#

Upload the video to Replay. The AI engine will analyze the video and reconstruct the UI as a set of React components.

Step 3: Review and Refine#

Replay generates a working React application. You can review the generated code, make adjustments, and integrate it into your existing React project.

Here's an example of the kind of code Replay might generate for a simple text input field:

typescript
// Replay-generated React component for a text input field
import React, { useState } from 'react';

const TextInput = ({ label, initialValue }) => {
  const [value, setValue] = useState(initialValue || '');

  const handleChange = (event) => {
    setValue(event.target.value);
  };

  return (
    <div>
      <label>{label}</label>
      <input type="text" value={value} onChange={handleChange} />
    </div>
  );
};

export default TextInput;

This is a simplified example, of course. Replay can handle much more complex UI elements and interactions, automatically generating the necessary state management and event handlers.

Key Features that Set Replay Apart#

Replay offers a range of features specifically designed for modernizing legacy UIs:

• •Multi-Page Generation: Reconstruct entire application flows, not just individual pages.
• •Supabase Integration: Easily connect your React application to a modern backend.
• •Style Injection: Apply custom styles to match your existing design system.
• •Product Flow Maps: Visualize the user flows captured from the video recordings.

These features make Replay a powerful tool for bridging the gap between legacy and modern technology.

Replay vs. Traditional Screenshot-to-Code#

Let's be honest, screenshot-to-code tools have been around for a while, and they're tempting. But they're fundamentally limited. Here's a comparison:

💡 Pro Tip: Don't underestimate the power of capturing subtle animations and transitions in your video recordings. Replay can often replicate these details in the generated React code, adding a touch of polish to the modernized UI.

The Benefits of Behavior-Driven Reconstruction#

• •Preserve User Familiarity: Maintain the core user flows that your users are already accustomed to.
• •Reduce Development Time: Automate the process of UI reconstruction, freeing up developers to focus on more complex tasks.
• •Improve Maintainability: Generate clean, modern React code that is easier to understand and maintain.
• •Reduce Risk: Avoid a complete rewrite, which can be risky and time-consuming.
• •Accelerate Digital Transformation: Modernize your UI without disrupting your existing business processes.

From Legacy to Leading Edge: A Real-World Scenario#

Imagine a large financial institution with a decades-old mainframe application used for processing loan applications. The application's UI is text-based and difficult to use, leading to errors and inefficiencies. A complete rewrite would be a massive undertaking, with a high risk of failure.

Using Replay, the institution can:

1. •Record videos of loan officers using the existing application.
2. •Upload the videos to Replay.
3. •Replay automatically generates a modern React UI that replicates the core functionality of the mainframe application.
4. •The institution can then integrate the new UI with its existing backend systems, providing a modern user experience without a complete rewrite.

⚠️ Warning: While Replay excels at reconstructing UI elements and interactions, it's important to remember that it's not a magic bullet. You may still need to manually adjust the generated code to fine-tune the user experience or integrate with specific backend systems.

Step-by-Step Guide: Modernizing a Legacy Form with Replay#

Let's walk through a more detailed example of modernizing a legacy form using Replay. We'll assume you have a video recording of a user filling out the form.

Step 1: Project Setup#

Create a new React project using Create React App or your preferred React framework.

bash
npx create-react-app my-modern-form
cd my-modern-form

Step 2: Upload and Analyze with Replay#

Upload the video recording to Replay. Replay will analyze the video and generate a set of React components that represent the form.

Step 3: Integrate the Generated Code#

Download the generated code from Replay and integrate it into your React project. This might involve copying the component files into your

directory and importing them into your main application component.

Step 4: Connect to Your Backend#

Modify the generated code to connect to your backend API. This might involve adding

calls or using a library like Axios to send data to your server.

typescript
// Example of connecting the form to a backend API
import React, { useState } from 'react';

const MyForm = () => {
  const [formData, setFormData] = useState({});

  const handleSubmit = async (event) => {
    event.preventDefault();
    try {
      const response = await fetch('/api/submit', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify(formData),
      });
      const data = await response.json();
      console.log('Success:', data);
    } catch (error) {
      console.error('Error:', error);
    }
  };

  return (
    <form onSubmit={handleSubmit}>
      {/* Form fields generated by Replay will go here */}
      <button type="submit">Submit</button>
    </form>
  );
};

export default MyForm;

Step 5: Style and Customize#

Apply custom styles to the generated components to match your existing design system. You can use CSS, CSS-in-JS, or a UI library like Material UI or Ant Design.

📝 Note: Replay's style injection feature can help automate this process by allowing you to specify a CSS file or theme that should be applied to the generated components.

Frequently Asked Questions#

Is Replay free to use?#

Replay offers different pricing plans, including a free tier with limited functionality. Paid plans offer more features and higher usage limits. Check the Replay website for the most up-to-date pricing information.

How is Replay different from v0.dev?#

While both Replay and v0.dev aim to generate code from visual inputs, Replay focuses specifically on video as the source of truth. This allows Replay to understand user behavior and reconstruct complex interactions, whereas v0.dev primarily uses static screenshots or design specifications.

What types of legacy applications can Replay handle?#

Replay can handle a wide range of legacy applications, including those built with technologies like Java Swing, VB6, and legacy web frameworks. The key is to have a video recording of a user interacting with the application.

What if the video quality is poor?#

While Replay works best with high-quality video recordings, it can often still extract useful information from lower-quality videos. Experiment with different recording settings to find what works best for your application.

Can I use Replay to generate code for mobile applications?#

Currently, Replay is primarily focused on web applications. However, the underlying technology could potentially be adapted for mobile applications in the future.

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Ready to try behavior-driven code generation? Get started with Replay - transform any video into working code in seconds.