Isomorphic JavaScript Applications — the Future of the Web?

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One of the best known mottos around the web is Java’s Write once, run everywhere. But does this motto apply to Java only? Can we use it to describe JavaScript too? The answer is Yes.

In this article, I’ll introduce you to the concept of isomorphic JavaScript applications, describing what they are and pointing to resources that help you develop this kind of application.

How We Arrived Here

Many years ago, the web was a bunch of static pages made with HTML and CSS without much interactivity. Each user action required the server to create and serve a complete page. Thanks to JavaScript, developers started to create nice effects, but it was with the advent of Ajax that a revolution started. Web developers began to write code that could communicate with the server to send and receive data without the need to reload the page.

As the years have passed, the responsibilities of the client-side code have grown a lot, resulting in a new type of application known as the single-page application (SPA). In an SPA, all the necessary assets are retrieved with a single page load, or dynamically loaded and added to the page as necessary. Some examples of SPAs are Gmail and the StackEdit editor.

SPAs allow for better interactivity, because almost all their operations are executed on the client, keeping communications with the server to a bare minimum. Unfortunately, they also have some major problems. Let’s discuss some of them.


Because SPAs require more client-side code than static pages, the amount of data to download is increased. This leads to slower initial loading times, which can have drastic consequences – such as frustrated end users and loss of revenue. According to one Microsoft article

A Bing study found that a 10ms increase in page load time costs the site $250K in revenue annually.


Because single-page applications rely on JavaScript execution, servers don’t produce all the HTML content they used to. Therefore, web crawlers have a lot of difficulties indexing pages. These crawlers are programs that make requests to a web server and analyze the result as raw text, without interpreting and executing the content like a typical browser running JavaScript would do. Recently, Google improved its web crawler so that it can work with JavaScript-based pages, but what about Bing, Yahoo, and all the other search engines? Good indexing is crucial for any business, as it usually leads to more visits and higher revenue.

Isomorphic JavaScript Applications

Isomorphic JavaScript applications are applications written in JavaScript that can run both on the client and on the server. Because of this, you can write the code once and then execute it on the server to render static pages and on the client to allow for fast interactions. So, this approach takes the best of the two worlds and lets you avoid the two issues described before.

Today there are several frameworks that assist you in developing this kind of application. One of them – possibly the most well-known – is Meteor. Meteor is an open-source JavaScript framework, written on top of Node.js, that focuses on real-time web applications. Another project I want to mention is Rendr. It’s a small library developed by Airbnb that allows you to run Backbone.js applications on both the client and the server.

More companies are adopting Node.js for their products. Sharing code between the client and server is becoming a more common and natural choice, and in my opinion is the future of web development. This trend is enhanced by sharing templates through libraries like React.


In this article I’ve introduced you to the concept of isomorphic JavaScript applications, a new approach to developing applications that combines the best of server-side and client-side programming. We’ve also discussed what problems this approach tries to solve, and some projects that you can employ today to embrace this philosophy.

Had you already heard of isomorphic JavaScript applications? Have you developed one? What was your experience?

Frequently Asked Questions about Isomorphic JavaScript Applications

What are the key benefits of using Isomorphic JavaScript?

Isomorphic JavaScript, also known as Universal JavaScript, offers several benefits. Firstly, it provides a seamless user experience by rendering pages on the server, which is faster than client-side rendering. This results in quicker page loads, improving user engagement and satisfaction. Secondly, it enhances SEO performance as search engine crawlers can easily index server-rendered pages. Lastly, it allows developers to use the same code on both the server and client side, reducing the complexity of the codebase and making it easier to maintain and debug.

How does Isomorphic JavaScript improve SEO?

Traditional JavaScript applications render content on the client-side, which can be challenging for search engine crawlers to index. Isomorphic JavaScript, on the other hand, renders pages on the server-side, making the content readily available for crawlers. This improves the visibility of the website on search engine results pages, leading to increased organic traffic.

Can Isomorphic JavaScript be used with any JavaScript framework?

Yes, Isomorphic JavaScript can be used with any JavaScript framework that supports server-side rendering. This includes popular frameworks like React, Angular, and Vue.js. However, the implementation details may vary depending on the specific framework.

What are the challenges of implementing Isomorphic JavaScript?

While Isomorphic JavaScript offers numerous benefits, it also comes with its own set of challenges. These include increased complexity in code management, potential performance issues due to server-side rendering, and the need for developers to have a deep understanding of both client-side and server-side environments.

How does Isomorphic JavaScript enhance user experience?

Isomorphic JavaScript enhances user experience by providing faster page loads. Since the pages are rendered on the server, they are delivered to the user’s browser fully formed, reducing the time it takes for the page to become interactive. This results in a smoother, more engaging user experience.

Is Isomorphic JavaScript the same as Universal JavaScript?

Yes, Isomorphic JavaScript and Universal JavaScript are two terms for the same concept. Both refer to JavaScript applications that can run both on the client-side and the server-side.

How does Isomorphic JavaScript contribute to code reusability?

Isomorphic JavaScript allows developers to write code that can run both on the client-side and the server-side. This means that the same code can be reused across different parts of the application, reducing the amount of code that needs to be written and maintained.

What is the future of Isomorphic JavaScript?

The future of Isomorphic JavaScript looks promising. With the increasing demand for high-performance, SEO-friendly web applications, more and more developers are turning to Isomorphic JavaScript. Furthermore, with the continuous improvement of JavaScript frameworks that support server-side rendering, it’s likely that the adoption of Isomorphic JavaScript will continue to grow.

How does Isomorphic JavaScript work with APIs?

Isomorphic JavaScript can work with APIs in the same way as traditional JavaScript. The difference is that with Isomorphic JavaScript, API calls can be made either from the client-side or the server-side, depending on where the code is running.

Can Isomorphic JavaScript be used for mobile app development?

While Isomorphic JavaScript is primarily used for web application development, it can also be used for mobile app development. Frameworks like React Native allow developers to write Isomorphic JavaScript code that can run on both web and mobile platforms.

Aurelio De RosaAurelio De Rosa
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I'm a (full-stack) web and app developer with more than 5 years' experience programming for the web using HTML, CSS, Sass, JavaScript, and PHP. I'm an expert of JavaScript and HTML5 APIs but my interests include web security, accessibility, performance, and SEO. I'm also a regular writer for several networks, speaker, and author of the books jQuery in Action, third edition and Instant jQuery Selectors.

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