How do you use developer tools and debugging techniques to troubleshoot and fix front-end issues?

While most developers are familiar with the basics of browser DevTools, such as inspecting elements, viewing console logs, or checking network requests, several advanced features and techniques can significantly improve your debugging efficiency and workflow. The Performance panel in DevTools allows you to record and analyze the runtime performance of your web page. The Coverage tool helps you detect unused CSS and JavaScript on your page. The Device Mode in DevTools lets you emulate various screen sizes and resolutions for testing the responsiveness of your designs. Integrated into Chrome DevTools, Lighthouse provides automated audits for performance, accessibility, SEO, and more.

When discussing developer tools for debugging frontend applications, the basic and most common method is to use the inspect element feature. In Chrome, you can also click on the toggle device toolbar to inspect defects for various screen sizes. If we are specifically referring to React, we have React DevTools to identify components and Redux DevTools to thoroughly monitor state changes, record them, and use them based on the developer's requirements.

Debugging frontend applications can involve a variety of techniques to identify and resolve issues. 1. Console Logging: Use console.log() statements to output variable values, function calls, and messages at different points in your code. This helps track the flow of execution and identify potential issues. 2. Debugger : Insert debugger statements in the code where you want to create breakpoints in the application. When the browser encounters the breakpoint/debugger , it will pause the page execution & allow developers to inspect the page based on their requirements. 3. Linters: Integrate linters into the development workflow to provide warnings in the form of log statements to the console. and you can customise them based on your needs

Apart from adding console.log in actual code we can directly add a log point which is similar to break point directly in browser dev tools source. Also when a breakpoint is active we can directly use dev tools console to print any value.

Step-by-Step Debugging; Breakpoints: Set breakpoints in your JavaScript code to pause execution at specific points. Watch Expressions: Monitor the values of specific variables or expressions. Call Stack: Inspect the call stack to see the sequence of function calls that led to the current point in execution.

The dreadful "Uncaught TypeError: Cannot read properties of undefined (reading ___)" is a super common one for new JS devs. This is a "null pointer" essentially, where the the variable you are trying to access has not been defined yet. It may be an order of operations or it may be that the variable was cleared out. The real thing to find here is why the thing being accessed is not defined. Same goes for if the variable is null. "Uncaught TypeError: Cannot read properties of null"

Some additional tools and techniques: Use the Performance tab to record and analyze the runtime behavior of your application. Look for long-running tasks, high memory usage, and other performance issues. Perform accessibility audits using tools like Lighthouse to ensure your application is usable by people with disabilities. Use tools to scan for security vulnerabilities or potential threats, such as cross-site scripting (XSS) or insecure content. Document any issues and solutions for future reference. Clear documentation helps in maintaining and updating the codebase efficiently. Collaborate with team members to review and discuss potential solutions, as fresh perspectives can often lead to faster problem resolution.

Determine the severity of the problem by assessing its impact on the user experience and business goals. Critical issues that prevent users from accessing key features should be prioritized over minor visual inconsistencies. Use browser DevTools to inspect the elements, CSS styles, and network requests involved in the issue. If the issue is complex, try isolating it by disabling certain CSS rules, JavaScript functions, or external resources to see if the problem persists. Use performance auditing tools like Lighthouse to ensure that your fix hasn’t negatively impacted load times or user experience. To avoid similar issues in the future, consider adding tests to your codebase that cover the scenario that caused the problem.

To effectively troubleshoot and fix front-end issues, follow a systematic approach that involves identifying, locating, and resolving problems. Use Developer Tools: Inspect your page and check the console for errors or warnings. Inspect Elements: Check HTML and CSS for issues. Network Requests: Ensure all resources load correctly. Console.log Statements: Log variable values to trace code behavior. Breakpoints: Pause execution to inspect the current state.

Es importante destacar la utilidad de herramientas como ESLint y Prettier en el desarrollo de software. La primera enfocada en la identificación y corrección de errores, así como en la aplicación de estándares de codificación. Por otro lado, Prettier se encarga del formateo automático del código, asegurando que mantenga una estructura legible y coherente. Al integrar estas herramientas en el proceso de desarrollo, se garantiza un código más limpio y coherente

The best practices of front-end coding, are using up-to-date technologies, using debugging tools, and researching and understanding open-source application architectures. There are many documents to understand which methods, and functions are up-to-date for JavaScript and have cross-browser capability, for example, if you need to check the latest array functions, MDN Web Docs is the best way to research it. If you need to check website performance on the local development process, you can use Google Lighthouse, you can reach it on your browser's developers tool tab. Also, you can use GitHub to research open-source applications.

Another thing we can consider for a large scale project is to use some typed framework over JavaScript. (Eg: Typescript, Flow). This will significantly help in reducing the runtime JavaScript errors, help keep the code clean and predictable.