How JavaScript Impacts Page Loading Speed on Mobile


Building a smart structure for your website is essential to its success. While many building blocks go into constructing a successful website – from content creation to on-page SEO optimisation, your site must use optimised server pages and CSS coding.

It is no secret that consumers increasingly turn to their mobile devices for browsing the web and interacting with brands. For example, an annual insights report showed that a whopping 75% of internet users own a smartphone and spend more time on their mobiles than desktops. Simply put, you need to control your clients’ experience on mobile devices to stand out from competitors. How do you do that?

Page loading speeds on mobiles can be negatively impacted by the generally increased file sizes of JavaScript files. This article will help you understand how they affect a site’s performance and what you can do to improve it.


The web is an increasingly JavaScript-driven world. The proliferation of single-page applications has made JavaScript even more critical on the web than it already was.

And yet, mobile devices tend to be slow in processing JavaScript. This can have a significant impact on your site’s user experience. The various ways JavaScript affects page loadings speeds on mobiles:

JavaScript is a programming language used by websites to enhance their functionality. It is used for many things, such as adding interactivity and animations.

This can be done with either JavaScript or CSS3. The difference between the two is that CSS3 uses HTML elements, so it is faster to load and parse than JavaScript, which must be downloaded before it can be executed.

It is prolonged and cumbersome to load compared to HTML or CSS. Because of its size, a larger JavaScript file takes longer to load and parse. This may not seem like much, but if you consider having hundreds of files, each weighing more than 100kb, this could result in a lot of time wasted just loading them all up.

JavaScript has become essential to many websites because it allows developers to add dynamic functionality without writing code for each element. For example, JavaScript can display information based on a user’s location or what they are searching for (for example, Google search results).

This provides users with more relevant content than standard static pages would do, but it also comes at a cost – namely, page loading times.

Using multiple JavaScript files rather than one significantly affects page load speeds because each file needs to be downloaded separately before it can be executed. While this might not seem like much at first glance, think about having ten separate files instead of just one large one – this will affect your website speed!

How to Reduce Page Load Time in JavaScript?

The average mobile page load time is approximately 27.3 seconds, 50% longer than the average desktop page load time. This is a massive problem for both users and businesses.

Users are frustrated by slow page loads and might not return to your site. Businesses lose revenue when users leave their sites before completing a purchase or sign-up process.

Page loading speed has become a significant factor in search engine rankings. The more your website loads, the better it will perform in search results.

The result of slow page load times is an increase in bounce rate — the percentage of visitors who leave your site after viewing only one page. A high bounce rate signals to Google that you’re not providing relevant content, which can negatively impact your search rankings.

While many factors affect page loading speed, JavaScript is one of the most significant. Google now penalises websites that use too much JavaScript or execute it too slowly.

Here are some ways you can reduce the impact of JavaScript on your site’s performance:

·         Create An Optimal Page Load Strategy

This means setting up your site so that content is loaded in the correct order and only when needed. This includes:

Reducing the number of HTTP requests by combining resources (e.g., images, scripts, stylesheets) into one or even a few files. This makes your pages load faster since less time is spent making requests, waiting for them to transfer and being processed by the browser. The fewer files there are to download, the less time it’ll take to load them all — especially if they’re large, like images or videos.

·         Minify and Compress JavaScript Files

Minification removes unnecessary characters from code to reduce its size without affecting its functionality (aka “uglifying”).

Compression is about converting files into smaller formats like ZIP archives or PNGs that can be sent over HTTP connections more efficiently than uncompressed files. Distributing means moving these resources from our servers onto CDNs (Content Delivery Networks) that are closer to users geographically, so their downloads are faster too!

·         Parse and compile JavaScript before execution

JavaScript execution is often one of the most resource-intensive tasks in modern browsers. It involves parsing, compiling, and executing code that could be hundreds of lines long on every page load. The more complex your code is and the more resources it requires to run smoothly (e.g., images), the slower your web pages load on mobile devices with limited memory or CPU power.

Mobile pages are notorious for taking a long time to load. According to Google, 53% of mobile users abandon a site that takes more than 3 seconds to load.

But why is it so slow? The answer lies in the way we use JavaScript on mobile.

Most websites use dynamic content loading via AJAX requests or JavaScript. This is because they have complex layouts and need to load data dynamically based on user interactions. This can cause issues when multiple requests happen simultaneously, which slows down the page loading time.

The solution to this problem is simple: reduce the number of requests needed by using asynchronous requests.

·         Use asynchronous requests

Asynchronous requests do not block other resources from loading while waiting for their results. This means they can be executed in parallel with other tasks without delaying them by blocking the main thread. Use Promises instead of callbacks. They are used everywhere in JavaScript, from jQuery to NodeJS and everything in between. They ensure that your code runs after an operation completes (or fails). Still, they also add another level of complexity regarding asynchronous code execution. When working with AJAX requests, you must be careful about how many callbacks you nest inside each other. Otherwise, your application might start running into problems like memory leaks or deadlocks.

Wrapping Up

The bottom line is that using JavaScript on your web pages can set a precedent for how much time your mobile users will have to wait and how functional your website will be on all devices. You can opt to hire a Java Developer, but, above all, you should take the time to understand how JavaScript impacts loading times and implement it carefully.

Leave a Comment