Data-Driven UI Refactoring: How to Prune 50k Lines of Dead Frontend Logic via Workflow Analysis

The average enterprise codebase is a digital graveyard. Hidden within your monolithic frontend are thousands of lines of "ghost logic"—conditional rendering for features decommissioned in 2018, edge-case handlers for browsers that no longer exist, and CSS declarations that style nothing. When you are staring down a 50,000-line legacy file, the risk isn't just the technical debt; it’s the $3.6 trillion global tax on productivity that prevents your team from shipping meaningful features.

Traditional refactoring fails because it relies on human intuition and incomplete documentation. Industry experts recommend a shift toward observability-based modernization. Instead of guessing what to delete, we must look at what users actually do. This is where datadriven refactoring prune lines becomes a surgical operation rather than a guessing game. By using Replay to record real user workflows, architects can finally map visual output to the underlying logic, identifying exactly which 30% of the code is actually providing value.

TL;DR:

• •The Problem: 67% of legacy systems lack documentation, leading to "fear-based" development where dead code is never deleted.
• •The Solution: Visual Reverse Engineering via Replay allows you to record user workflows and automatically generate documented React components.
• •The Impact: Reduce refactoring time from 40 hours per screen to just 4 hours, saving 70% in total modernization costs.
• •The Strategy: Use workflow analysis to identify active code paths and prune dead logic with surgical precision.

---

The $3.6 Trillion Ghost: Why Manual Refactoring Fails#

According to Replay's analysis, 70% of legacy rewrites fail or exceed their initial timeline. The reason is simple: you cannot refactor what you do not understand. In a typical financial services or healthcare application, the frontend has evolved over a decade. Developers have come and gone, leaving behind a "spaghetti" of dependencies.

When you attempt to datadriven refactoring prune lines manually, you encounter the "Chesterton’s Fence" of software engineering. You see a complex

block and want to delete it, but you don't know why it was put there. Without documentation—which is missing in 67% of enterprise systems—you leave the code in place "just in case." Over five years, this "just in case" logic balloons into 50,000 lines of unmaintainable debt.

Video-to-code is the process of capturing a live user interface session and programmatically converting the visual elements and state transitions into clean, modular code.

By using Visual Reverse Engineering, teams can bypass the need for ancient documentation. Replay records the actual execution of the UI, providing a "truth source" that manual audits can never replicate.

---

The Methodology: Datadriven Refactoring Prune Lines via Workflow Analysis#

To prune 50k lines of dead logic, you need a data-driven map. You don't start with the source code; you start with the user.

Step 1: Workflow Capture (The "Truth" Phase)#

Instead of reading through

, record the critical paths. Whether it’s a loan application flow in a banking portal or a patient check-in system in healthcare, Replay captures every state change, API call, and visual transition. This creates a "Flow"—a documented map of the architecture as it exists in the real world, not as it was intended ten years ago.

Step 2: Visual Mapping and Component Discovery#

Once the flows are captured, Replay’s AI Automation Suite analyzes the recording. It identifies recurring patterns and UI clusters. This is where the datadriven refactoring prune lines process gains momentum. If a specific logic branch in your legacy code is never triggered during a comprehensive recording of all production workflows, it is a prime candidate for pruning.

Step 3: Generating the "Clean" State#

Instead of trying to fix the old code, Replay allows you to generate a modern React equivalent of the observed behavior. You aren't "translating" the old code (which would just move the mess to a new framework); you are "re-implementing" the observed requirements using modern patterns.

---

Technical Implementation: From Bloat to React#

Let’s look at a concrete example. Imagine a legacy jQuery-based "Member Portal" component. It’s 2,500 lines long, handles its own XHR requests, and has dozens of global variables.

The Legacy Mess (Before)#

typescript
// A simplified version of a 2,500-line legacy file
// Problem: Mixed concerns, dead logic, and global state pollution
var currentMember = null;
var isEligible = false; // Is this still used? 

function initPortal(data) {
    if (data.status === 'ACTIVE') {
        $('#status-icon').addClass('green');
        // Logic for a legacy "Silver Plan" that was discontinued in 2021
        if (data.planCode === 'SILVER_2021') {
            renderSilverLegacyDashboard(); 
        }
    }
    // 400 lines of DOM manipulation follow...
    // ...
    // ...
    bindEvents();
}

function bindEvents() {
    $('.btn-submit').on('click', function() {
        // More spaghetti...
    });
}

When you use Replay's AI Automation Suite, the system ignores the unused

logic because it never sees it rendered in the recorded workflows. It extracts the core functionality and generates a clean, type-safe React component.

The Modernized Component (After Replay Extraction)#

tsx
import React from 'react';
import { useMemberData } from './hooks/useMemberData';
import { StatusBadge } from './components/StatusBadge';
import { MemberDashboard } from './components/MemberDashboard';

/**
 * Modernized Member Portal
 * Generated via Replay Visual Reverse Engineering
 * Pruned: Legacy PlanCode logic, manual DOM manipulation
 */
export const MemberPortal: React.FC<{ memberId: string }> = ({ memberId }) => {
  const { data, loading, error } = useMemberData(memberId);

  if (loading) return <Spinner />;
  if (error) return <ErrorMessage message="Failed to load portal" />;

  return (
    <div className="p-6 max-w-4xl mx-auto">
      <header className="flex justify-between items-center mb-8">
        <h1 className="text-2xl font-bold">Member Portal</h1>
        <StatusBadge status={data.status} />
      </header>
      
      <MemberDashboard 
        member={data.member} 
        activeFeatures={data.enabledFeatures} 
      />
    </div>
  );
};

By focusing on the datadriven refactoring prune lines approach, the resulting code is 90% smaller. The logic for the "Silver Plan" is gone because it wasn't present in the data-driven analysis of the live system.

---

Why Workflow Analysis is the Key to Pruning#

The biggest challenge in enterprise modernization is the "18-month average rewrite timeline." Most projects die in the "Analysis" phase. Teams spend six months just trying to document what the current system does.

Industry experts recommend moving away from manual "code archaeology." Instead of reading the code to find the requirements, use Replay Flows to visualize the architecture. When you record a workflow, Replay builds a blueprint of the application's state machine.

The "Pruning" Logic#

1. •Identify the Core: Capture 100% of standard user journeys.
2. •Define the Perimeter: Anything outside these journeys is flagged as "Potential Dead Logic."
3. •Validate: Check the flagged logic against edge-case recordings.
4. •Extract: Use Replay's Blueprints to export the validated logic into a new Design System.
5. •Decommission: Safely delete the 50k lines of legacy code, knowing your modern React library covers 100% of the observed surface area.

This is how you move from an 18-month timeline to a matter of weeks. You aren't refactoring; you are extracting the soul of the application and giving it a new body.

---

Datadriven Refactoring Prune Lines in Regulated Industries#

For Financial Services, Healthcare, and Government, the stakes are higher. You can't just "move fast and break things." You need an audit trail.

Replay is built for these environments. With SOC2 compliance, HIPAA-readiness, and On-Premise deployment options, the datadriven refactoring prune lines process remains secure. When you record a workflow in a sensitive environment, Replay can handle data masking to ensure PII (Personally Identifiable Information) never leaves your secure zone.

According to Replay's analysis, regulated industries see the highest ROI from visual reverse engineering. These organizations often have the oldest technical debt ($3.6 trillion global impact) and the strictest requirements for documentation. Replay provides the automated documentation they’ve been missing for decades.

Learn more about Modernizing Legacy Systems in Regulated Industries

---

Implementation Details: Using Replay's Library and Blueprints#

The transition from a 50k-line monolith to a clean component library requires a structured repository. Replay’s Library feature acts as your "Modern State." As you record flows and extract components, they are organized into a central Design System.

Example: Component Extraction Workflow#

1. •Record: A developer records the "Account Settings" page.
2. •Analyze: Replay identifies a "Profile Card," a "Password Reset Form," and a "Notification Toggle."
3. •Blueprints: The developer opens the Replay Blueprint editor to fine-tune the generated TypeScript props.
4. •Export: The components are pushed to the Replay Library, ready to be imported into the new React project.

typescript
// Example of a Replay-generated Blueprint configuration
export const ProfileCardBlueprint = {
  componentName: "ProfileCard",
  observedProps: ["userName", "email", "avatarUrl", "lastLogin"],
  stateTransitions: ["editMode", "saving", "error"],
  dependencies: ["@ui/button", "@ui/input"],
  // Datadriven refactoring prune lines logic:
  // Only export logic observed in the "Account Settings" Flow
  pruneUnusedStyles: true,
  generateUnitTests: true
};

---

Frequently Asked Questions#

How does datadriven refactoring prune lines differ from standard static analysis?#

Static analysis looks at code references to see if a function is "called." However, in legacy systems with a lot of dynamic dispatch or string-based event naming, static analysis often reports that everything is "used." Data-driven refactoring via workflow analysis looks at the execution and visual output. If the code runs but never changes the UI or the state in a meaningful way for the user, it is effectively dead and can be pruned.

Can Replay handle complex state management like Redux or Vuex?#

Yes. Replay’s visual reverse engineering doesn't just look at the DOM; it hooks into the state transitions. By analyzing the flow of data through the system, Replay can reconstruct the state logic in modern React hooks or any state management library you prefer, ensuring that the datadriven refactoring prune lines process doesn't break your business logic.

What happens to edge cases that aren't captured in a recording?#

This is a common concern. Replay allows for "Coverage Recording," where QA teams or automated test suites run through all known edge cases. By combining production workflow recordings with QA edge-case recordings, you create a comprehensive map. If logic isn't hit in either of those, it is a 99.9% certainty that the code is dead.

Is the code generated by Replay actually maintainable?#

Unlike "black-box" AI code generators, Replay produces code based on your specific design tokens and architectural patterns. Because it uses the Blueprints system, you have full control over the output style (e.g., Tailwind vs. Styled Components, Functional vs. Class components). It’s not just "code that works"; it’s "code that follows your team's standards."

---

Conclusion: The End of Fear-Based Development#

Technical debt is a weight that slows down every sprint. When you are afraid to delete code, your application becomes a museum of past mistakes. By adopting a datadriven refactoring prune lines strategy, you replace fear with data.

With Replay, the daunting task of modernizing a 50,000-line frontend becomes a structured, visual process. You save 70% of the time usually wasted on manual analysis, and you ensure that the new system is documented, type-safe, and—most importantly—free of the ghosts of legacy past.

Ready to modernize without rewriting? Book a pilot with Replay