Transform Legacy UI Code into Modern Frameworks with AI

TL;DR: Replay leverages AI to reconstruct legacy UI code from video recordings, enabling modernization into frameworks like React with behavior-driven accuracy.

Modernizing legacy UI code is a daunting task. Years of accumulated technical debt, undocumented features, and outdated frameworks can make even simple updates a nightmare. Rewriting from scratch is often considered, but the risk of introducing regressions or missing crucial functionality looms large. The challenge isn't just about translating code; it's about understanding why the UI behaves the way it does.

The Problem: Understanding Legacy UI Behavior#

Traditional approaches to UI modernization often focus on static analysis or manual reverse engineering. These methods struggle to capture the dynamic behavior of complex applications. You might be able to decipher the code, but understanding the intended user flows and edge cases remains elusive.

Consider this scenario: You're tasked with migrating a legacy web application built with jQuery to React. The original developers are long gone, and the codebase is a tangled mess of event handlers and DOM manipulations. How do you ensure that the new React components accurately replicate the original functionality, including subtle interactions and error handling?

The Solution: Behavior-Driven Reconstruction with Replay#

Replay offers a revolutionary approach to UI modernization by leveraging AI to analyze video recordings of user interactions. Instead of relying solely on static code analysis, Replay uses "Behavior-Driven Reconstruction" to understand the intended behavior of the UI. This means that Replay doesn't just see pixels; it understands user actions, data flows, and application state transitions.

Here's how Replay helps transform legacy UI:

1. •Capture User Flows: Record videos of users interacting with the legacy UI, demonstrating key features and workflows.
2. •AI-Powered Analysis: Replay analyzes the video, identifying UI elements, user actions, and data inputs. Gemini powers the reconstruction engine.
3. •Code Generation: Replay generates clean, modern code (e.g., React components) that accurately replicates the observed behavior.
4. •Refinement and Integration: Review and refine the generated code, integrate it into your modern application, and iterate on the process.

Key Features of Replay for UI Modernization#

Replay provides several key features that streamline the UI modernization process:

• •Multi-Page Generation: Reconstruct complex, multi-page applications from a single video recording.
• •Supabase Integration: Seamlessly integrate with Supabase for data persistence and authentication in your modern application.
• •Style Injection: Apply consistent styling to the generated code, ensuring a cohesive look and feel across your application.
• •Product Flow Maps: Visualize user flows and application state transitions to gain a deeper understanding of the legacy UI.

Replay vs. Traditional Approaches#

📝 Note: Manual reverse engineering can be effective, but it's time-consuming and requires specialized expertise. Screenshot-to-code tools are limited by their inability to understand user behavior. Replay offers a balance between speed, accuracy, and understanding.

Example: Migrating a Legacy jQuery Form to React#

Let's say you have a legacy jQuery form that handles user registration. The form includes several input fields, validation logic, and AJAX calls to a backend API. Migrating this form to React manually would involve deciphering the jQuery code, rewriting the validation logic, and implementing the API calls using

or .

With Replay, you can simply record a video of yourself filling out the form, triggering different validation errors, and submitting the form successfully. Replay will then generate a React component that accurately replicates the form's behavior, including the validation logic and API calls.

Here's a simplified example of the React code that Replay might generate:

typescript
import React, { useState } from 'react';

const RegistrationForm = () => {
  const [name, setName] = useState('');
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [error, setError] = useState('');

  const handleSubmit = async (e) => {
    e.preventDefault();

    if (!name || !email || !password) {
      setError('Please fill in all fields.');
      return;
    }

    try {
      const response = await fetch('/api/register', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({ name, email, password }),
      });

      if (!response.ok) {
        throw new Error('Registration failed.');
      }

      // Handle successful registration
      console.log('Registration successful!');
    } catch (err) {
      setError(err.message);
    }
  };

  return (
    <form onSubmit={handleSubmit}>
      {error && <p className="error">{error}</p>}
      <label htmlFor="name">Name:</label>
      <input type="text" id="name" value={name} onChange={(e) => setName(e.target.value)} />
      <label htmlFor="email">Email:</label>
      <input type="email" id="email" value={email} onChange={(e) => setEmail(e.target.value)} />
      <label htmlFor="password">Password:</label>
      <input type="password" id="password" value={password} onChange={(e) => setPassword(e.target.value)} />
      <button type="submit">Register</button>
    </form>
  );
};

export default RegistrationForm;

This code is a starting point, and you can further refine it to match your specific requirements. However, Replay significantly reduces the initial effort and ensures that the core functionality of the form is preserved.

Step-by-Step Guide to Modernizing UI with Replay#

Here's a simplified guide to using Replay for UI modernization:

Step 1: Record User Flows#

Use a screen recording tool to capture videos of users interacting with the legacy UI. Focus on demonstrating key features, workflows, and edge cases.

💡 Pro Tip: Use a high-quality screen recorder and ensure clear audio narration to provide additional context for Replay.

Step 2: Upload and Analyze Video#

Upload the video to Replay. Replay will analyze the video and identify UI elements, user actions, and data inputs.

Step 3: Review and Refine#

Review the generated code and make any necessary refinements. You can adjust the code, styling, and data bindings to match your specific requirements.

Step 4: Integrate into Modern Framework#

Integrate the generated code into your modern application. You can use the code as a starting point and further customize it as needed.

⚠️ Warning: While Replay significantly reduces the effort involved in UI modernization, it's important to thoroughly test the generated code to ensure that it meets your quality standards.

Step 5: Iterate and Improve#

Iterate on the process by recording additional user flows and refining the generated code. As you gain more experience with Replay, you'll be able to streamline the UI modernization process even further.

Benefits of Using Replay#

• •Reduced Development Time: Replay automates the code generation process, saving you significant time and effort.
• •Improved Accuracy: Replay understands user behavior, ensuring that the generated code accurately replicates the original functionality.
• •Lower Risk: Replay minimizes the risk of introducing regressions or missing crucial functionality during UI modernization.
• •Enhanced Understanding: Replay provides valuable insights into the behavior of the legacy UI, helping you make informed decisions about modernization.
• •Faster Time to Market: By accelerating the UI modernization process, Replay helps you bring new features and improvements to market faster.

Frequently Asked Questions#

Is Replay free to use?#

Replay offers a free tier with limited features and usage. Paid plans are available for more extensive use and advanced features. Check the Replay pricing page for details.

How is Replay different from v0.dev?#

While both tools aim to generate code from visual input, Replay focuses on video as the primary input and emphasizes behavioral understanding. V0.dev relies more on static screenshots and component libraries. Replay's video-based approach allows it to capture dynamic interactions and user flows that are difficult to represent with static images.

What frameworks does Replay support?#

Replay currently supports React, Vue, and Angular, with plans to add support for more frameworks in the future.

How accurate is the generated code?#

The accuracy of the generated code depends on the quality of the video recording and the complexity of the UI. However, Replay typically generates code that is highly accurate and requires minimal refinement.

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