How Replay Captures Hidden Modal State Logic for Modern React Apps

Enterprise software is dying under the weight of its own UI. If you work in financial services or healthcare, you likely manage a "modal graveyard"—thousands of pop-ups, nested dialogs, and hidden validation layers built on jQuery, ASP.NET, or early Angular. These aren't just UI elements; they are complex state machines. When you try to modernize, these modals become the single biggest point of failure because their logic is invisible to traditional code scrapers.

According to Replay's analysis, 67% of legacy systems lack any form of technical documentation, and modals represent the most significant "documentation gap." Developers spend weeks trying to figure out which global variables trigger a specific "Submit" button or why a background overlay fails to clear. This manual reverse engineering is why 70% of legacy rewrites fail or exceed their original timelines.

Replay changes this by treating the UI as the source of truth. Instead of reading broken code, Replay watches the application in motion.

TL;DR: Legacy modals contain hidden state logic that manual audits often miss. Replay captures hidden modal behaviors by recording real user workflows and using Visual Reverse Engineering to convert those interactions into documented React components. This cuts the average time per screen from 40 hours down to 4, saving enterprises up to 70% on modernization costs.

Why Replay Captures Hidden Modal Logic Better Than Manual Audits#

Traditional modernization involves a developer sitting with a legacy app, opening the DevTools, and trying to trace a spaghetti-tangle of event listeners. This is a recipe for technical debt. Industry experts recommend moving away from manual "code-first" discovery toward "behavior-first" extraction.

Video-to-code is the process of converting visual recordings of software interactions into functional, production-ready frontend code. Replay pioneered this approach to bypass the mess of legacy source files.

When Replay captures hidden modal states, it isn't just taking a screenshot. It tracks the lifecycle of the component:

1. •Trigger Conditions: What state change (Redux, local, or global) caused the modal to appear?
2. •Input Dependencies: Which fields are required before the "Save" button enables?
3. •Z-Index and Layering: How does the modal interact with the DOM hierarchy?
4. •Dismissal Logic: Does the state reset on "Close," or does it persist?

Manual reverse engineering takes roughly 40 hours per complex screen. With Replay, that same screen is documented and converted into a React Blueprint in under 4 hours.

The Cost of Missing Hidden State#

The global technical debt crisis has reached $3.6 trillion. Much of this is locked in "hidden" logic. If a developer misses a single validation rule inside a legacy insurance claim modal, the new React app will ship with data integrity bugs that cost thousands to fix post-launch.

How Replay Captures Hidden Modal State in Legacy Financial Systems#

Financial services apps are notorious for "nested state." You might have a modal for "New Transaction" that opens another modal for "Address Verification." Tracking this via source code is a nightmare because the logic is often split across multiple legacy files or stored in global window objects.

Visual Reverse Engineering is the automated extraction of UI patterns and business logic from video recordings of a running application. Replay uses this to map out the "Flows" of your architecture.

When a user records a workflow, Replay’s AI Automation Suite identifies the modal boundaries. It sees the transition from a background state to an active overlay. Because Replay captures hidden modal transitions frame-by-frame, it can reconstruct the exact React state needed to replicate that behavior.

Example: Legacy jQuery Modal to React#

Consider a legacy modal that uses global variables to track "dirty" states. A developer might miss that the "X" button triggers a specific cleanup function.

Legacy Mess (jQuery/Pseudo-code):

javascript
// Hidden logic buried in a 5,000 line file
$('#modal-save').on('click', function() {
  if (window.GLOBAL_VAL_CHECK === true && $('#user-email').val() !== "") {
    submitData();
    closeModal();
    window.isDirty = false;
  } else {
    alert("Error!");
  }
});

Clean React Output from Replay: Replay identifies these behaviors and generates a structured React component with clear props and state management.

typescript
import React, { useState, useEffect } from 'react';
import { Modal, Button, TextField } from '@/components/ui';

interface TransactionModalProps {
  isOpen: boolean;
  onClose: () => void;
  initialCheck: boolean;
}

export const TransactionModal: React.FC<TransactionModalProps> = ({ 
  isOpen, 
  onClose, 
  initialCheck 
}) => {
  const [email, setEmail] = useState('');
  const [isSubmitDisabled, setIsSubmitDisabled] = useState(true);

  // Replay captured that the button only enables when email is present
  useEffect(() => {
    setIsSubmitDisabled(!(initialCheck && email.length > 0));
  }, [email, initialCheck]);

  return (
    <Modal open={isOpen} onClose={onClose}>
      <TextField 
        label="User Email" 
        value={email} 
        onChange={(e) => setEmail(e.target.value)} 
      />
      <Button 
        disabled={isSubmitDisabled} 
        onClick={() => console.log('Submitting...')}
      >
        Save Transaction
      </Button>
    </Modal>
  );
};

By using the Replay Blueprint Editor, architects can refine this generated code, ensuring it fits the new enterprise design system while preserving the original business rules.

The Replay Method: Record → Extract → Modernize#

We have coined a specific methodology for handling legacy debt: The Replay Method. This three-step process ensures that no logic is left behind in the old system.

1. Record (Behavioral Capture)#

Subject Matter Experts (SMEs) or QA testers record themselves performing standard tasks in the legacy app. This is the "source of truth." If the app allows a user to bypass a modal by clicking the backdrop, Replay sees it. If a modal only appears under specific data conditions, Replay logs it.

2. Extract (Visual Reverse Engineering)#

Replay’s engine analyzes the video. It identifies components, typography, spacing, and—most importantly—state transitions. This is where Replay captures hidden modal interactions that are otherwise invisible to static analysis tools. It builds a "Flow" map showing how users move from the main dashboard into these sub-states.

3. Modernize (Code Generation)#

The extracted data is pushed into the Replay Library. From here, you generate documented React components. You aren't just getting a "look-alike" UI; you're getting a component that understands its own requirements.

For more on this, read our guide on Legacy Modernization Strategy.

Solving the "Z-Index" and "Portal" Problem#

In modern React, modals are usually handled via Portals to avoid CSS clipping issues. In legacy apps (especially those built 10+ years ago), modals were often just

tags hidden with and forced to the top with .

When you try to move this to a modern stack, the CSS often breaks. Replay captures hidden modal layout properties and translates them into modern CSS-in-JS or Tailwind classes. It recognizes that a specific element is acting as an overlay and suggests a modern

primitive from your new Design System.

This level of automation is why the average enterprise rewrite timeline drops from 18 months to just a few weeks of active development.

Behavioral Extraction vs. Static Analysis#

Why can't you just use an AI to read your old code? Because legacy code is often "dead." According to industry research, up to 30% of legacy codebases consist of functions that are never actually called.

Static analysis tools will try to modernize everything, including the bugs and the dead code. Replay only modernizes what is actually used. By recording real workflows, you ensure that the new React app is a streamlined version of the old one, not a 1:1 migration of technical debt.

Behavioral Extraction is the process of identifying functional requirements by observing how an application responds to user input in real-time. This is the core engine behind how Replay captures hidden modal logic.

Automated Component Libraries are the end result of this process. Instead of building a button 50 times, Replay identifies the pattern once and creates a reusable asset.

Security and Compliance in Regulated Industries#

For our clients in Government, Telecom, and Insurance, security is a non-negotiable. You cannot send sensitive financial data to a public cloud AI for "analysis."

Replay is built for these environments:

• •SOC2 & HIPAA Ready: Your recordings and generated code are handled with enterprise-grade security.
• •On-Premise Available: For high-security environments, Replay can run entirely within your firewall.
• •PII Scrubbing: Our AI Automation Suite can detect and redact sensitive information from recordings before they are processed.

When Replay captures hidden modal data, it focuses on the structure and logic, not the sensitive PII (Personally Identifiable Information) typed into the fields.

The Future of Video-First Modernization#

We are moving toward a world where the "manual rewrite" is seen as a relic of the past. The $3.6 trillion technical debt problem cannot be solved by humans typing faster. It requires a shift in how we perceive software.

Replay is the first platform to use video for code generation. It is the only tool that generates full component libraries from user interactions. By focusing on the visual layer, we bypass the "black box" of legacy backend code and focus on what actually matters: the user experience.

Modernizing Complex Workflows#

If you are dealing with a multi-step modal wizard—common in healthcare for patient onboarding—the logic is incredibly dense.

• •Step 1: Patient Info
• •Step 2: Insurance (Hidden if "Self-Pay" is selected)
• •Step 3: Consent Forms

A manual auditor might miss the conditional logic of Step 2. But because Replay captures hidden modal transitions based on user selection, the resulting React code will include the necessary conditional rendering logic out of the box.

typescript
// Replay-generated conditional logic for a multi-step modal
const PatientWizard = () => {
  const [step, setStep] = useState(1);
  const [isSelfPay, setIsSelfPay] = useState(false);

  // Replay detected this transition logic from the recording
  const handleNext = () => {
    if (step === 1 && isSelfPay) {
      setStep(3); // Skip Insurance step
    } else {
      setStep(step + 1);
    }
  };

  return (
    <div>
      {step === 1 && <StepOne onSelectSelfPay={setIsSelfPay} />}
      {step === 2 && <InsuranceStep />}
      {step === 3 && <ConsentStep />}
      <button onClick={handleNext}>Next</button>
    </div>
  );
};

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 code. It uses Visual Reverse Engineering to extract UI components, state logic, and design tokens from recordings of real user workflows. Unlike generic AI tools, Replay is purpose-built for enterprise modernization, offering a 70% time savings over manual rewrites.

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

Modernizing a Mainframe or COBOL system often involves a "Screen Scraping" approach, but this lacks modern component structure. The best way to modernize these systems is to use Replay to record the terminal emulator or legacy web wrapper in action. Replay captures the behavioral logic of the old system and converts it into a modern React Design System, allowing you to build a new frontend that communicates with the legacy backend via APIs.

How does Replay handle complex state inside modals?#

Replay captures hidden modal state by analyzing the visual changes that occur during user interaction. It monitors how buttons enable/disable, how validation messages appear, and how data persists across different views. This behavioral data is then used to generate React hooks and state variables that mirror the original application's logic without requiring access to the original, often obfuscated, source code.

Can Replay work with desktop applications?#

Yes. While Replay is optimized for web-based legacy systems (ASP.NET, Java Spring, PHP, etc.), its Visual Reverse Engineering engine can process any video recording. This makes it a powerful tool for migrating legacy desktop software to modern web-based React platforms.

Is Replay SOC2 and HIPAA compliant?#

Yes. Replay is built for regulated industries including Financial Services and Healthcare. We offer SOC2 compliance, HIPAA-ready data handling, and the option for on-premise deployment to ensure that your modernization process meets all security requirements.

Ready to modernize without rewriting? Book a pilot with Replay