https://RustRocket.rs -- Cloud Monk Losang Jinpa, Ph.D., MCSE / MCT, https://Rustaceans.rs, Full Stack Cloud Native Rust DevOps Engineer - Rocket Framework Rust Microservices on Kubernetes-AWS-Azure-GCP

Troubleshooting JavaScript
Part 1: The Basics of Investigating a Codebase
- Revealing an App’s Obscurities
- Understanding Your App’s Logic Through Debugging Techniques
Part 2: Deep Analysis of an App’s Execution
- Identifying Resource Consumption Problems
Part 3: Finding Problems in Large Systems
Popular Debugging and Troubleshooting Libraries
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Troubleshooting JavaScript

Return to Troubleshooting React, Troubleshooting Programming Languages, Debugging JavaScript, JavaScript Programming Mistakes and Code Smells

Part 1: The Basics of Investigating a Codebase

Revealing an App’s Obscurities

When facing unexpected output, the first step is to clarify the app's behavior. This involves understanding why an app produces unexpected output, clarifies slowness, or crashes unexpectedly. Tools like console.log statements and debuggers can be invaluable in revealing what part of the code is executing unexpectedly.

Understanding Your App’s Logic Through Debugging Techniques

Debugging is crucial for understanding an app's logic. Techniques include:

Using a debugger to pause execution and inspect variables.
Understanding the stack trace to see the function call flow.
Setting conditional breakpoints to halt execution under specific conditions.
Remote debugging allows inspection of apps running on servers or other devices.
Analyzing exception stack traces to identify method calls leading to errors.
Measuring execution time with timing functions to pinpoint slowness.
In multithreaded architectures, investigating issues requires special considerations like monitoring thread interactions.
Logging is fundamental for recording runtime information, and it's important to manage log persistence, levels, and frameworks effectively.
Avoiding problems caused by excessive logging involves strategic planning and utilizing logging frameworks efficiently.

Part 2: Deep Analysis of an App’s Execution

Identifying Resource Consumption Problems

Profiling is essential for detecting abnormal usage of resources. Tools and techniques include:

Using profilers to observe CPU and memory usage.
Identifying memory leaks and database connection problems.
Call graphs help in understanding code design and execution flow.
In multithreaded applications, monitoring and analyzing thread locks, waiting threads, and investigating deadlocks with thread dumps are crucial for maintaining performance.
Heap dumps are a powerful tool for finding memory leaks and other memory-related issues.

Part 3: Finding Problems in Large Systems

Large systems pose unique challenges due to their complexity and scale. Techniques for troubleshooting include:

Investigating service communication through HTTP server probes and HTTP client probes.
Monitoring low-level events on sockets for network issues.
Utilizing integrated log monitoring and deployment tools for comprehensive oversight.
Implementing fault injection to replicate and study complex issues.
Using mirroring to facilitate error detection and testing in a controlled environment.

Popular Debugging and Troubleshooting Libraries

1. Chrome DevTools: A comprehensive set of web developer tools built directly into the Google Chrome browser, offering powerful resources for debugging and optimizing web applications.

2. Firebug: Although discontinued, Firebug was a pioneering tool that laid the groundwork for modern debugging tools. Alternatives such as the Firefox Developer Tools have incorporated and expanded upon its functionality.

3. Node.js Inspector: An asynchronous debugger for Node.js applications, allowing inspection and control of scripts running in the Node.js environment.

4. Visual Studio Code Debugger: Integrated into the Visual Studio Code editor, this debugger supports a wide range of programming languages and frameworks, making it versatile for web development.

5. Webpack: Primarily a module bundler, Webpack also offers features for debugging modern web applications by managing assets and modules with care.

Each of these tools has its alternatives, such as WebStorm for an IDE with integrated debugging, or Rollbar and Sentry for error tracking and monitoring. The choice depends on specific project requirements and developer preferences. ```

This format covers the essentials of troubleshooting and debugging JavaScript applications, from basic techniques to more advanced strategies for dealing with complex systems, and concludes with a brief overview of popular tools and libraries in the field.