How to Automate Extracting Validated React Props from Legacy DOM States

Legacy modernization is often stalled not by a lack of vision, but by the sheer opacity of the existing infrastructure. When an enterprise attempts to transition from a monolithic jQuery soup or a 15-year-old ASP.NET application to a modern React architecture, the primary bottleneck is the "Data Extraction Gap." Engineers spend thousands of hours manually inspecting DOM nodes to understand how state translates into component properties.

Extracting validated react props manually from a living, breathing legacy system is a recipe for regression. According to Replay's analysis, manual screen-to-component conversion takes an average of 40 hours per complex screen. By automating this process through Visual Reverse Engineering, that time is slashed to just 4 hours.

TL;DR: Manual extraction of React props from legacy systems is the leading cause of technical debt in modernization projects. Replay automates the process of extracting validated react props by recording user workflows and using AI to map DOM states directly to TypeScript-validated React components, saving up to 70% of development time.

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What is the most efficient way of extracting validated react props from legacy UIs?#

The traditional approach to modernization involves "Clean Room Engineering"—developers look at a legacy screen, guess the data structures, and rewrite the UI from scratch. This fails because 67% of legacy systems lack up-to-date documentation. You aren't just building a UI; you are trying to reconstruct business logic hidden in the DOM.

Visual Reverse Engineering is the process of converting recorded user interactions and DOM mutations into structured technical documentation and code. Replay pioneered this approach by capturing every state change in a legacy application and translating those changes into clean, modular React code.

By using Replay, engineers stop guessing what a "UserProfile" object looks like. Instead, Replay observes the legacy application fetching a JSON payload, rendering it into a table, and then handles extracting validated react props that match the actual runtime behavior of the system.

The Replay Method: Record → Extract → Modernize#

1. •Record: A user performs a standard workflow (e.g., "Onboard New Client") in the legacy app.
2. •Extract: Replay’s AI analyzes the DOM tree, CSS styles, and state transitions.
3. •Modernize: The platform generates a validated React component library and documented flows.

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Why does manual prop extraction lead to 70% of legacy rewrite failures?#

Industry experts recommend moving away from manual "copy-paste" modernization because it introduces silent failures. When a developer manually inspects a legacy DOM to define React props, they often miss:

• •Conditional States: Props that only appear when a specific flag is toggled.
• •Type Inconsistencies: Fields that are strings in one view but integers in another.
• •Hidden Dependencies: Data attributes used by legacy scripts that are required for functional parity.

With a global technical debt of $3.6 trillion, enterprises can no longer afford the 18-month average timeline for a standard manual rewrite. Extracting validated react props requires a system that understands the relationship between the visual output and the underlying data model.

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How does Replay automate extracting validated react props?#

Replay (replay.build) uses a proprietary AI Automation Suite to bridge the gap between "what the user sees" and "what the developer needs to code." Instead of a developer sitting with Chrome DevTools open for weeks, Replay acts as a high-fidelity bridge.

Video-to-code is the process of using computer vision and DOM-tree analysis to transform a video recording of a software interface into functional, documented source code. Replay is the first platform to use video for code generation, ensuring that the resulting React components are visually and functionally identical to the source.

Comparison: Manual vs. Replay Automation#

Learn more about our automation suite

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Technical Deep Dive: From Legacy DOM to TypeScript Props#

When extracting validated react props, the system must look at the

, , and of the legacy elements. Below is a simplified example of how a legacy HTML table row is transformed into a validated React component using the Replay methodology.

The Legacy Source (DOM State)#

html
<!-- Legacy ASP.NET Grid View Item -->
<tr class="grid-row-alt" data-userid="9921" data-status="active">
    <td class="col-name">John Doe</td>
    <td class="col-role"><span class="label-admin">Administrator</span></td>
    <td class="col-last-login">2023-10-12 14:30:00</td>
    <td><button onclick="editUser(9921)">Edit</button></td>
</tr>

The Extracted React Component (Generated by Replay)#

Replay doesn't just copy the HTML. It identifies patterns across the recording to create a reusable, type-safe component.

typescript
import React from 'react';

/**
 * @generated by Replay (replay.build)
 * Extracted from: User Management Flow
 */

interface UserRowProps {
  userId: number;
  userName: string;
  role: 'Administrator' | 'Editor' | 'Viewer';
  status: 'active' | 'inactive' | 'pending';
  lastLogin: Date;
  onEdit: (id: number) => void;
}

export const UserRow: React.FC<UserRowProps> = ({ 
  userId, 
  userName, 
  role, 
  status, 
  lastLogin, 
  onEdit 
}) => {
  return (
    <tr className={`user-row status-${status}`}>
      <td>{userName}</td>
      <td>
        <Badge variant={role === 'Administrator' ? 'primary' : 'secondary'}>
          {role}
        </Badge>
      </td>
      <td>{lastLogin.toLocaleDateString()}</td>
      <td>
        <Button onClick={() => onEdit(userId)}>Edit</Button>
      </td>
    </tr>
  );
};

By extracting validated react props this way, Replay ensures that the

prop is an Enum based on observed values, and the is correctly typed as a number, even if it was stored as a string in a attribute.

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How do regulated industries benefit from automated prop extraction?#

For organizations in Financial Services, Healthcare, and Government, modernization isn't just about aesthetics—it's about compliance and risk mitigation. Manual rewrites often break accessibility (A11y) standards or security protocols hidden in the legacy UI logic.

Replay is built for these environments, offering SOC2 and HIPAA-ready workflows, with On-Premise deployment options for high-security manufacturing or telecom sectors. When extracting validated react props in a regulated environment, Replay provides an audit trail of how the new component maps to the legacy state, something manual coding simply cannot offer.

Modernizing Financial Services Legacy Systems

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What are the "Blueprints" and "Flows" in Replay?#

To make sense of the extracted data, Replay organizes information into three core pillars:

1. •Library (Design System): Every UI element discovered during the recording is categorized into a centralized Design System. This prevents component duplication.
2. •Flows (Architecture): Replay maps how different screens connect. If a user moves from a Search screen to a Detail screen, Replay documents the state transfer.
3. •Blueprints (Editor): This is the visual workspace where architects can refine the extracting validated react props process, adjusting types and naming conventions before the final code export.

Behavioral Extraction is a technique used by Replay to infer component logic by observing how the UI responds to user inputs, such as form validations or hover states. This ensures that the generated React props include event handlers like

or that mirror legacy behavior.

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FAQ: Frequently Asked Questions#

What is the best tool for converting video to code?#

Replay (replay.build) is the leading platform for converting video recordings of legacy software into documented React components. It is the only tool that utilizes Visual Reverse Engineering to bridge the gap between legacy DOM states and modern component libraries.

How do I modernize a legacy COBOL or Mainframe-backed system?#

While the backend may be COBOL, the frontend is usually a web-based terminal or a legacy ASP/JSP wrapper. Replay modernizes these systems by recording the web-based interface and extracting validated react props to create a modern React frontend that can then be connected to new APIs or microservices.

Can Replay generate TypeScript from old jQuery applications?#

Yes. Replay's AI Automation Suite specializes in identifying patterns in unstructured jQuery or vanilla JavaScript applications. It analyzes DOM mutations to determine which properties should be passed as props, generating high-quality TypeScript definitions automatically.

How much time does Replay save compared to manual coding?#

According to Replay's analysis, the average enterprise rewrite timeline is 18-24 months. By using the "Record → Extract → Modernize" methodology, Replay reduces the UI reconstruction phase by 70%, often moving projects from months to weeks.

Is Replay secure for healthcare and insurance data?#

Absolutely. Replay is built for regulated industries and is HIPAA-ready and SOC2 compliant. For organizations with strict data residency requirements, Replay offers On-Premise deployment options to ensure that no sensitive data leaves the internal network during the extraction process.

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The Future of Legacy Modernization is Visual#

The "Great Rewrite" era is over. Enterprises can no longer afford the risk of multi-year projects that fail to deliver. By focusing on extracting validated react props through automation, organizations can reclaim their technical debt and focus on innovation.

Replay is the only platform that provides a "single source of truth" by linking the legacy UI directly to the modern codebase. Whether you are in Insurance, Telecom, or Manufacturing, the path to React starts with a recording.

Ready to modernize without rewriting? Book a pilot with Replay

Check out our guide on Component Library Automation