Inefficient Application Analysis wit Tools and Devtools 🚀

This repository demonstrates common memory leaks, inefficiencies, and performance issues in React applications. It serves as a practical tool to showcase how to identify, debug, and fix these problems using Chrome DevTools tools, including Lighthouse, Performance, Memory, Network, Record, Coverage, and Source tabs.

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Features

1. Leaky Components

• LeakyTimer.tsx: Demonstrates a memory leak caused by an uncleared setTimeout.
• LeakyInterval.tsx: Simulates a memory leak due to an unhandled setInterval.
• LeakyListener.tsx: Illustrates a memory leak resulting from an unremoved resize event listener on the window object.

2. Inefficient Rendering

• Components like RecipeCard.tsx and IngredientCard.tsx include inefficiencies such as redundant re-renders and unnecessary computations.

3. Unused Code

• Includes examples of:
  • Unused CSS rules in components like RecipeList.tsx.
  • Unused functions or state variables across multiple components.

4. Component Architecture

• Components such as RecipeHeader.tsx, InstructionStep.tsx, and RecipeBanner.tsx highlight modularity and reusability, but also showcase potential inefficiencies.

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How to Use This Application

1. Clone the Repository

git clone https://github.com/helabenkhalfallah/tools-devtools-app-analysis.git
cd tools-devtools-app-analysis

2. Install Dependencies

pnpm install

3. Run the Application

pnpm dev

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Objectives

This application allows you to:

1. Analyze Memory Leaks:

   • Use the Memory tab to identify retained objects, detached DOM nodes, and closures.

2. Evaluate Application Performance:

   • Use the Performance, Lighthouse, and Record tabs to analyze rendering times, bottlenecks, and resource usage.

3. Detect Unused Code:

   • Use the Coverage and Source tabs to locate unused CSS and JavaScript.

4. Inspect Network Activity:

   • Use the Network tab to debug API calls, analyze load times, and spot inefficient resource usage.

5. Analyze Bundle Size:

   • Vite Bundler Analyzer (pnpm analyze): Visualize the size of the app’s modules to identify oversized dependencies or inefficient packaging.
   • Bundlephobia: Check the size, treeshaking support, and dependency impact of npm packages used in the app.

6. Assess Webpage Loading:

   • WebPageTest: Run comprehensive tests on your webpage to measure real-world performance, including loading speed, render times, and third-party resource impact.

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Key Components

Leaky Components

Component	Issue	Description
LeakyTimer.tsx	setTimeout not cleared	Timeout holds a reference to state after unmounting.
LeakyInterval.tsx	setInterval not cleared	Interval continues to update state after unmounting.
LeakyListener.tsx	Event listener not removed	resize listener retains a reference to the component state.

Recipe Components

Component	Purpose	Notes
RecipeHeader.tsx	Displays recipe metadata	Modular and reusable.
IngredientCard.tsx	Renders individual ingredients	Contains rendering inefficiencies.
InstructionStep.tsx	Shows step-by-step instructions	Could be optimized further.
RecipeList.tsx	Lists all recipes	Demonstrates potential coverage issues.

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How to Analyze Issues

1. Detect Memory Leaks

1. Open Chrome DevTools.
2. Navigate to the Performance tab:
   • Click "Record" and interact with the app (e.g., toggling leaky components or navigating between views).
   • Look for a continuously growing JS Heap size, which may indicate memory leaks.
3. Use the Memory tab:
   • Take a heap snapshot and analyze retained objects, closures, and detached DOM nodes.

2. Identify Unused Code

1. Open Chrome DevTools and navigate to the Coverage tab:
   • Click "Start Instrument Coverage and Reload Page" to begin recording.
   • Interact with the app (e.g., navigating or triggering components).
2. Observe the report:
   • CSS: Look for rules that are not applied during interactions.
   • JavaScript: Identify functions or scripts that are loaded but never executed.
3. Export the coverage report to analyze large, unused files for optimization.

3. Debug Rendering Inefficiencies

1. Open the Performance Tab in Chrome DevTools:
   • Click "Record" and perform app interactions (e.g., scrolling, clicking, or navigating).
2. Analyze the timeline:
   • Look for long tasks or repeated layout shifts.
   • Identify components with slow rendering or excessive re-renders.
3. Use Flame Charts:
   • Pinpoint functions or components consuming the most time.

4. Inspect Network Activity

1. Open the Network Tab in Chrome DevTools:
   • Reload the app and monitor network requests.
2. Analyze API calls:
   • Check for failed or unnecessary requests.
   • Monitor response times and payload sizes.
3. Optimize resource loading:
   • Identify large or unoptimized assets (e.g., images, JavaScript bundles).
   • Ensure HTTP caching is utilized for static files.

5. Analyze Bundles and Dependencies

1. Use Vite Bundler Analyzer (pnpm analyze):
   • Visualize the size of individual modules in your bundle.
   • Identify oversized dependencies or unused packages.
2. Use Bundlephobia:
   • Analyze npm packages to detect size, treeshaking support, and dependency impact.
   • Replace heavy or unused packages with lighter alternatives if possible.

6. Assess Overall Page Performance

1. Run Lighthouse in Chrome DevTools:
   • Analyze metrics such as Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and Total Blocking Time (TBT).
   • Review optimization recommendations, such as eliminating render-blocking resources or optimizing images.
2. Use WebPageTest:
   • Evaluate real-world page loading speeds and resource loading patterns.
   • Compare results across multiple geographic locations for better insights.

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Fixing Issues

Issue	Solution
Uncleared Timers	Use clearTimeout or clearInterval in useEffect cleanup functions.
Unremoved Listeners	Use removeEventListener in useEffect cleanup functions.
Unused Code	Remove unused CSS and dead JavaScript code.
Inefficient Rendering	Use React.memo, useCallback, and useMemo to optimize rendering.

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Tools for Debugging

1. Chrome DevTools:
   • Lighthouse Tab: Evaluate app performance and discover optimization suggestions.
   • Performance Tab: Analyze memory leaks and heap usage.
   • Coverage Tab: Detect unused code.
   • Network Tab: Inspect API and resource performance.
   • Source Tab: Review the source code and debug issues.

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Example Fix: Clearing a Timer

Here’s an example of how to fix a memory leak in LeakyTimer.tsx:

useEffect(() => {
    const timeoutId: NodeJS.Timeout = setTimeout(() => {
        setMessage("Timeout Finished!");
    }, 5000);

    return () => {
        clearTimeout(timeoutId); // Cleanup to prevent leaks
    };
}, []);

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Conclusion

This application is a demonstration of common issues:

• Memory leaks
• Inefficient rendering
• Unused code

It serves as a learning tool to better understand how to identify, debug, and fix these issues in real-world applications.

Feel free to fork the repo and experiment further!

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