Web Performance Optimization by cleaning up Unnecessary JavaScript

Web performance Optimization

A website’s performance is no longer just a technical concern—it can be a business game-changer. Without Web Performance Optimization, 53% of mobile site visits are abandoned. Since a page takes longer than three seconds to load (as reported by Google), the impacts of inefficient JavaScript can be far-reaching. Slow loading times result in user dissatisfaction, decreasing traffic, and conversion rates, which ultimately lead to loss of revenue.

Moreover, Google’s algorithm considers page speed while ranking websites, meaning a slow site can negatively affect your SEO, further reducing your visibility. In fact, according to Akamai, a 100-millisecond delay in load time can lower conversion rates by 7%.

Among the most prevalent culprits of web performance issues is unnecessary or inefficient JavaScript. Addressing this issue can lead to significant improvements in loading times, user experience, SEO rankings, and consequently, your bottom line.

In this blog, we will explore a range of strategies and tools that can help you identify and eliminate unnecessary JavaScript, boosting your website’s performance and positively impacting your business.

1. Diving Deep with Chrome DevTools

Chrome’s Developer Tools offer a comprehensive suite of debugging instruments, with the Performance tab being particularly useful for analyzing your site’s runtime performance. Here, you can record your page load and see when scripts are loaded, their loading time, and their impact on your page rendering. Analyzing these elements can give you a clear idea of where your JavaScript might be slowing things down.

2. Evaluating Code Use with Chrome DevTools Coverage

The Coverage Tab, another feature of Chrome DevTools, presents an overview of how much code is used versus how much is loaded. It provides a clear identification of scripts loaded but not used, pointing towards optimization by removing or deferring such scripts.

3. Harnessing the Power of Lighthouse

Lighthouse is a powerful open-source tool developed by Google for improving the quality of web pages. It provides audits for performance, accessibility, progressive web apps, SEO, and more. Running Lighthouse against your web page can offer a plethora of suggestions for enhancement, including potential JavaScript optimizations.

Running a Lighthouse audit is straightforward — you can do it directly in Chrome DevTools, from the command line, or as a Node module. Interpreting the results might take a bit more practice. Lighthouse provides a score for different aspects of your site (Performance, Accessibility, Best Practices, SEO, etc.), along with specific recommendations for improving these scores.

The challenge might come in understanding the technical details behind some of the recommendations, especially if you’re new to web performance optimization. Google provides extensive documentation and guides to help you understand and implement the recommendations made by Lighthouse, which should ease the learning process.

4. Speeding Up with Google PageSpeed Insights

Google PageSpeed Insights is a tool that analyzes the content of a web page and generates suggestions to improve its speed. Each suggestion is accompanied by a list of scripts that might be causing the delay, offering direct insights into scripts that need your attention.

The tool is fairly straightforward and doesn’t require extensive technical knowledge to use, but understanding how to implement some of the suggestions could require a bit more experience with web development and performance optimization.

Google PageSpeed Insights is quite proficient at identifying a variety of JavaScript-related issues that can hamper your page load speed. Here are some examples:

  1. Render-blocking JavaScript:

    Render-blocking JavaScript refers to scripts that prevent the page from displaying until they have finished loading. PageSpeed Insights can point these out, and the common solution is to defer or asynchronously load these scripts.

  2. Unused JavaScript:

    PageSpeed Insights can identify JavaScript code that’s loaded but never utilized. Removing or lazily loading these scripts can reduce network activity and improve page load times.

  3. JavaScript execution time:

    If JavaScript takes a long time to execute, it can slow down your page. PageSpeed Insights can indicate scripts that take a long time to process, suggesting you to optimize them for better performance.

  4. Large JavaScript payloads:

    Large files take longer to download and process. PageSpeed Insights can identify large JavaScript files and suggest strategies to minimize them, such as removing unnecessary code, compressing the file, or splitting the code into smaller, more manageable chunks.

  5. Main-thread work:

    The main thread is where a browser processes most tasks, including JavaScript execution. If there’s too much JavaScript for the main thread to process, it can slow down the page. PageSpeed Insights can identify when the main thread is overworked.

By identifying these issues, Google PageSpeed Insights provides actionable recommendations on how to resolve them and, consequently, how to boost your page’s speed and performance.

5. The Trial and Error Approach: Remove and Test

This approach might sound old-school, but it’s effective. If you suspect a script isn’t necessary, temporarily remove it and gauge the impact on your site performance and functionality. This can provide concrete evidence of whether a script is beneficial or detrimental.

6. Relying on Static Analysis Tools

Tools like ESLint help to analyze your JavaScript code without executing it, identifying potential performance issues such as unused variables or functions. These can indicate scripts that could be optimized or removed.

Optimizing JavaScript is a journey that requires continuous effort. By regularly analyzing your scripts using these tools and strategies, you can ensure your web pages perform at their best, providing an excellent user experience and boosting your SEO rankings. Remember, a high-performing, fast-loading webpage not only pleases users but also ranks higher in search engine results.

Unleash the power of web performance optimization today by trimming and optimizing your JavaScript load. Happy coding!

Related blog: We have a separate blog written for cleaning up WordPress websites for better performance.

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