Hermann Kao@itishermann
May 4, 2021 11:21 AM

How to Debug Your Javascript Code Like a Pro

An introduction to the javascript debugging techniques

Tags: Javascript

Debugging is an essential part of the software development process. It helps developers identify and fix errors in their code, ensuring that the application runs smoothly and meets the desired functionality. Debugging also helps developers understand how their code works and how it interacts with other components of the application. Without proper debugging, it can be challenging to identify and fix issues, leading to a poor user experience and potentially damaging the reputation of the application. Therefore, it is crucial to understand the importance of debugging and to use the right tools and techniques to debug your code effectively.

Common mistakes in debugging

Debugging is an essential part of the development process, but it’s not always easy. There are some common mistakes that developers make when debugging their JavaScript code. One of the most common mistakes is not using console.log() statements effectively. Another mistake is not understanding the scope of variables and functions. It’s also important to avoid making assumptions about the code and to test each part of it thoroughly. By avoiding these common mistakes and using effective debugging techniques, you can save time and frustration in the development process.

Understanding the problem

Reproducing the error

Reproducing the error is an essential step in debugging your JavaScript code. It involves identifying the exact conditions that trigger the error and replicating them in a controlled environment. This can be done by using tools like the browser console, debugging tools, or even by manually testing the code. Once you have successfully reproduced the error, you can then start analyzing the code to identify the root cause of the problem. This step is crucial in ensuring that you fix the error permanently and prevent it from occurring again in the future.

Identifying the root cause

Identifying the root cause of a bug is crucial in debugging your Javascript code. One effective way to do this is by using console.log statements to track the flow of your code and identify where the bug is occurring. Another helpful technique is to use breakpoints in your code to pause the execution at a specific point and inspect the values of variables and objects. Additionally, utilizing browser developer tools can provide valuable insights into the behavior of your code and help pinpoint the root cause of the bug. By identifying the root cause, you can then focus your efforts on fixing the specific issue and avoid wasting time on unrelated code.

Using browser tools

Console logging

Console logging is a powerful tool for debugging your JavaScript code. By using console.log(), you can output information to the console and see what’s happening in your code in real-time. This can be especially helpful when trying to track down errors or understand how your code is executing. You can also use console.log() to test specific parts of your code and make sure they’re working as expected. Just be sure to remove any console.log() statements before deploying your code to production, as they can slow down your application.


Debugger: One of the most powerful tools for debugging JavaScript code is the built-in debugger. The debugger allows you to pause the execution of your code at any point and inspect the values of variables, step through your code line by line, and even modify variables on the fly. To use the debugger, simply add the keyword “debugger” to your code where you want to pause execution. When your code reaches that point, it will pause and you can start inspecting and debugging your code. The debugger is an essential tool for any JavaScript developer, and mastering it can greatly improve your ability to find and fix bugs in your code.

Network tab

The Network tab in the browser’s developer tools is a powerful tool for debugging JavaScript code that interacts with the network. It allows you to see all the requests and responses made by your code, including the headers, status codes, and response bodies. This can be incredibly useful for identifying issues with API calls, network latency, and other network-related problems. By using the Network tab, you can quickly identify where your code is failing and make the necessary adjustments to fix the issue. Additionally, you can use the Network tab to optimize your code’s performance by identifying slow-loading resources and minimizing unnecessary requests. Overall, the Network tab is an essential tool for any JavaScript developer looking to debug their code like a pro.

Sources tab

The Sources tab in the browser’s developer tools is a powerful tool for debugging your JavaScript code. It allows you to view and edit the source code of your web page, set breakpoints, and step through your code line by line. You can also view the call stack and watch expressions to help you identify and fix errors in your code. Additionally, the Sources tab provides access to the Console, where you can log messages and interact with your code in real-time. By mastering the features of the Sources tab, you can become a pro at debugging your JavaScript code and ensure that your web applications are running smoothly.

Debugging techniques


Breakpoints are an essential tool for debugging your JavaScript code. By setting a breakpoint, you can pause the execution of your code at a specific line and inspect the values of variables and objects at that point in time. This can help you identify where your code is going wrong and make it easier to fix any issues. To set a breakpoint in your code, simply click on the line number in your code editor or use the debugger statement in your code. Once the breakpoint is set, you can run your code in debug mode and it will pause at the breakpoint, allowing you to step through your code and see what’s happening at each step.

Step-by-step execution

Step-by-step execution is a powerful technique for debugging your JavaScript code. By stepping through your code line by line, you can identify exactly where errors are occurring and gain a deeper understanding of how your code is working. To use this technique, you’ll need to use a debugger tool, such as the one built into your browser’s developer tools. Once you’ve set a breakpoint in your code, you can use the debugger to step through each line of code, inspecting variables and watching how they change as your code executes. With practice, you’ll be able to quickly identify and fix bugs in your code, making you a more efficient and effective developer.

Watch expressions

Watch expressions are a powerful tool for debugging your JavaScript code. By setting up a watch expression, you can monitor the value of a variable or expression as your code runs. This can be particularly useful when you’re trying to track down a bug that’s causing unexpected behavior in your code. With watch expressions, you can quickly identify when a variable’s value changes, and you can use this information to pinpoint the source of the problem. To set up a watch expression, simply right-click on a variable in your code and select “Add Watch Expression”. Then, enter the expression you want to monitor and click “OK”. The value of the expression will be displayed in the watch window as your code runs, allowing you to keep a close eye on it and catch any issues that arise.

Conditional breakpoints

Conditional breakpoints are a powerful tool that can help you debug your JavaScript code more efficiently. With conditional breakpoints, you can set a breakpoint that will only trigger when a certain condition is met. This can be incredibly useful when you’re trying to track down a specific bug or issue in your code. For example, you might set a conditional breakpoint that triggers only when a certain variable reaches a certain value. This can help you pinpoint exactly where the problem is occurring and make it easier to fix. To set a conditional breakpoint, simply right-click on the line of code where you want to set the breakpoint and select “Add Conditional Breakpoint”. Then, enter the condition that you want to trigger the breakpoint and you’re good to go!

Debugging common issues

Syntax errors

Syntax errors are one of the most common types of errors that developers encounter while writing Javascript code. These errors occur when the code violates the syntax rules of the language. The browser’s console will display an error message that indicates the line number and the type of error. To fix syntax errors, you need to carefully review your code and ensure that all the syntax rules are followed correctly. You can also use tools like linters and IDEs that provide real-time feedback on syntax errors. It’s important to fix syntax errors as soon as possible because they can prevent your code from running correctly and cause unexpected behavior.

Logic errors

Logic errors are one of the most common types of errors in Javascript code. These errors occur when the code does not produce the expected output due to a flaw in the logic of the program. To debug logic errors, it is important to carefully examine the code and identify any inconsistencies or incorrect assumptions. One effective technique is to use console.log statements to track the flow of the program and identify where the error occurs. Additionally, using a debugger tool can help to pinpoint the exact location of the error and provide insights into the state of the program at that point in time. By taking a systematic approach to debugging logic errors, developers can ensure that their code is functioning as intended and delivering the desired results.

Asynchronous code

Asynchronous code can be tricky to debug because it doesn’t always execute in the order it appears in your code. One way to tackle this is to use console.log statements to track the flow of your code. You can also use breakpoints in your browser’s developer tools to pause execution at specific points and inspect the state of your variables. Another helpful tool is the Promise.all() method, which allows you to wait for multiple asynchronous operations to complete before moving on to the next step in your code. By using these techniques, you can effectively debug your asynchronous code and ensure that it’s running smoothly.

Browser compatibility

Browser compatibility is a crucial aspect of web development, especially when it comes to Javascript. Different browsers may interpret the same code differently, leading to unexpected behavior and errors. To ensure that your code works seamlessly across all browsers, it’s important to test it thoroughly on different platforms and versions. You can use tools like BrowserStack or Sauce Labs to test your code on a wide range of browsers and devices. Additionally, you can use feature detection and polyfills to provide fallbacks for unsupported features. By prioritizing browser compatibility, you can ensure that your Javascript code works reliably for all users, regardless of their browser preferences.

Best practices

Testing your code

After writing your code, it’s important to test it thoroughly to ensure that it works as expected. One way to test your code is to use console.log statements to output values and check if they match your expectations. Another way is to use a testing framework like Jest or Mocha, which allows you to write automated tests that can be run repeatedly to ensure that your code is functioning correctly. It’s also important to test your code in different environments and browsers to ensure that it works consistently across all platforms. By testing your code thoroughly, you can catch and fix any bugs before they cause problems for your users.

Keeping your code clean

Keeping your code clean is crucial for efficient debugging. It is important to follow best practices and maintain a consistent coding style throughout your project. This includes using meaningful variable names, commenting your code, and organizing your code into logical sections. Additionally, removing unnecessary code and optimizing your code for performance can also help prevent bugs from occurring. By keeping your code clean, you can easily identify and fix issues, making the debugging process much smoother and faster.

Using version control

Using version control is an essential part of any software development process, including debugging JavaScript code. Version control systems like Git allow developers to keep track of changes made to their code, collaborate with others, and revert to previous versions if necessary. By using version control, you can easily identify when a bug was introduced and track down the specific changes that caused it. Additionally, version control can help you keep your code organized and maintain a clear history of your project’s development. Whether you’re working on a small personal project or a large team project, using version control is a crucial step in debugging your JavaScript code like a pro.

Collaborating with others

Collaborating with others is an essential aspect of software development, and debugging is no exception. When working with a team, it’s crucial to establish clear communication channels and a shared understanding of the codebase. One effective way to collaborate on debugging is to use a version control system like Git, which allows multiple developers to work on the same codebase simultaneously. Additionally, tools like code review platforms and collaborative debugging tools can help streamline the process and ensure that everyone is on the same page. By working together, developers can more efficiently identify and resolve issues, leading to a more robust and reliable codebase.


Summary of key points

In summary, debugging your JavaScript code is an essential skill for any developer. By following the key points outlined in this article, you can become a pro at debugging your code. Remember to use console.log() statements, breakpoints, and the debugger tool to identify and fix errors. Additionally, make sure to test your code thoroughly and seek help from online resources and communities when needed. With these tips and tricks, you can streamline your debugging process and become a more efficient and effective developer.

Encouragement to keep learning

Learning to debug your JavaScript code like a pro is a continuous process. It requires patience, persistence, and a willingness to learn from your mistakes. Don’t be discouraged if you encounter bugs that seem impossible to solve at first. Keep practicing and experimenting with different debugging techniques. As you gain more experience, you’ll become more confident in your abilities and be able to tackle even the most complex issues. Remember, every bug you solve is an opportunity to learn something new and improve your skills. So keep pushing yourself to learn and grow as a developer, and you’ll be well on your way to becoming a JavaScript debugging pro.

Next Steps: Now that you have learned some advanced techniques for debugging your JavaScript code, it’s time to put them into practice. Start by reviewing your existing code and identifying any potential bugs or errors. Use the tools and techniques discussed in this article to diagnose and fix these issues. For further guidance and support, be sure to check out the other posts, where you can find additional resources and connect with other developers. Don’t let debugging hold you back - with the right approach and mindset, you can overcome any challenge and build amazing applications.

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