Free React useEffect Memory Leak Simulator & Debugger

Overview

This interactive web utility helps developers visualize the impact of missing cleanup functions in React useEffect hooks. By simulating real-world scenarios—such as unstopped timers, dangling event listeners, and pending API calls—users can see exactly how memory leaks occur and how to resolve them using professional coding patterns.

Core Features

• Scenario Library: Select from common scenarios including setInterval leaks, window resize listeners, and async/await fetch operations.
• Interactive Visualizer: A visual monitor that tracks the 'Active Subscription Count' and 'Memory Pressure' of the simulated React lifecycle.
• Side-by-Side Comparison: View a 'Leaky' code block vs. a 'Fixed' code block with the cleanup function explicitly highlighted.
• Simulated Console: A real-time log that shows React mounting/unmounting events and specific side-effect triggers.
• Performance Impact Metrics: A dynamic graph showing how memory consumption grows over time in a leaked state compared to a cleaned state.

UI Layout

• Header: A clean, minimalist header displaying the app title and a 'Reset Simulation' button.
• Main Dashboard: A two-column interface:
  • Left Column (Controls): A selector for the simulation scenario, a 'Mount Component' toggle, and configuration inputs (e.g., interval delay).
  • Right Column (Visualizer): A code-viewer component showing the current logic, coupled with a graphical gauge that represents memory usage.
• Status Area: A floating console window at the bottom of the right column detailing internal React-style lifecycle events (e.g., "[Effect] Starting interval", "[Cleanup] Clearing interval").

Design & Aesthetics

• Palette: A professional light-mode aesthetic using shades of Slate, Cool Blue (for interaction), and Emerald (for healthy, cleaned states), with a cautionary Amber for detected leaks.
• Typography: Clean, sans-serif fonts (e.g., Inter or System-UI) for high readability.
• Transitions: Smooth fading animations when switching between simulation modes and gentle pulse animations for active timers.
• Responsiveness: A mobile-first design that stacks the dashboard on smaller screens and provides a side-by-side view on desktop monitors.

Technical Specifications

• Architecture: Pure HTML5, CSS3, and JavaScript, bundled into one file. The app will use the React UMD build via CDN to allow for native execution of the simulation logic.
• Memory Management: No use of localStorage, sessionStorage, or cookies. The simulation state is held entirely in a Javascript let variable or a React state object.
• Security: Sandboxed iframe compatibility. No external calls except the CDN script sources. All buttons and interactive elements must have semantic HTML tags for accessibility.
• Execution: The simulator will use setTimeout or setInterval to mock the browser lifecycle. It will be designed to stop all active loops when the 'unmount' button is triggered by the user to demonstrate the cleanup success.

Implementation Directives

1. Always Clear Intervals: The simulation code must enforce the use of clearInterval in the return statement of the hook.
2. Clean Design: Use Tailwind CSS (via CDN) for utility-first styling. Ensure all borders and shadows are soft and subtle.
3. Strict Constraints: Ensure the code does not attempt to access persistent storage. All data used for the visualization is local and volatile.
4. Accessibility: All interactive elements must have proper aria-labels and keyboard support for users navigating without a mouse.