What are some of the common web performance pitfalls and how can you avoid them?

Some of the ways that I found used Use Server-side rendering or Static Site Generation. Use ReactQuery to cache network requests.

While handling with many requests, using batch request technique helps. A solid caching strategy also needs to be in place. For static assets better to use a cdn.

Some of the way that found usedful Lazy components and large size pictures or videos. Always use optimized pictures as placeholder in initial rendering

An example to consider is what happens if the resource the page is trying to load becomes unavailable for some reason: firewalls, network outage, service goes down etc. In that case the loading cannot finish, and the page can be stuck in a state that it cannot recover from. However if those resources are loaded asynchronously, a fallback or retry can be added to put the application into a working state.

In my experience, a piece of code can always be better, no matter how good it is, it could be better on at least one of many different points of view, like readability, performance, reusability, verbosity, and many other specific to the logic that is being covered by that piece of code. Talking about "Efficient Code" specifically, the main focus is code performance, as software developers we should always think about how the code could be faster and/or consume fewer machine resources, for this, there are many techniques and core concepts that have better adoption depending on the complexity of the problem being solved in the code, then selecting the best approach is where the developer experience shows up and becomes very relevant ??.

Make a habit of revisiting your code or even get a 2nd (or 3rd) pair of eyes on it. I often write code that gets the job done to start, but then come back to it and see how it can be improved on. There's usually multiple ways to write a piece of code and the first iteration is rarely the best way.

Correct usage of cache control headers is one of the lowest hanging fruits you can grab. You don't need to get that immutable JSON blob from the server every time.

To measure and improve web performance, conducting a thorough website audit is key. Analyze usability, backend ease of use, performance, security, SEO, hosting infrastructure, and code deployment. Focus on performance optimization by enhancing website speed, optimizing images/videos, and minimizing JavaScript and CSS. Prioritize security by installing top-notch security plugins and protecting against attacks. Implement technical SEO strategies like improving page load time, HTML/CSS restructuring, and enhancing mobile user experience.

Understanding re-rendering conditions is vital for optimizing performance in any modern JavaScript library, such as React. Unnecessary re-renderings can be a significant drain on performance if not handled correctly. By employing concepts such as memoization, careful state management, and the judicious use of lifecycle methods or hooks, developers can control when and how often components re-render, reducing the overall computational cost and enhancing the user experience with smoother and faster interface interactions. Knowledge of these techniques is a key skill in modern front-end development, contributing to the creation of efficient, responsive, and high-performing web applications.