Single-Page Applications: A Comprehensive Guide

By Ben Eaton
Published on May 5, 2022
Single-Page Applications: A Comprehensive Guide

Single-page applications (SPAs) are a hot topic in the web development world. They're touted as the future of rich web experiences, and many developers have been quick to jump on board. However, if you're not careful, they can quickly become challenging to maintain - and even more importantly, it can be hard for users without JavaScript enabled to use your site. This blog post will discuss what single-page applications are and why they've become so popular, how SPAs work, their advantages and disadvantages, and finally, some guidelines about how best to create them.

What is a single-page application?

Whether you know it or not, you are almost certainly an avid user of single-page applications. SPAs are websites that load all their content into a single page instead of having to reload the entire page every time you navigate to a new section. This makes for a much smoother browsing experience and no more waiting for your website to refresh each time you click on a link.

SPAs work by using a technology called AJAX (Asynchronous JavaScript and XML) to load small bits of data from the server as needed. This means that only the content that has changed since your last visit is loaded, which drastically reduces the amount of data that needs to be transferred - and hence, the time it takes for your page to load.

It also has some other benefits: since all the code is loaded in one go, it's much faster and simpler to update a single-page application than a traditional website. This is especially true when using JavaScript libraries like React or Angular, which only require you to redeploy your code when you make changes - instead of refreshing the entire page, which can take minutes on a large website.

The advantages of SPAs

As with anything, there are pros and cons to using single-page applications. Here are some of the main advantages:

Speed and responsiveness

One of the best things about SPAs is how fast and responsive they are. Since only the changed portions of the page need to be refreshed, you'll see much less loading time when navigating from section to section. This is very important because, according to Google research, taking more than 200 milliseconds to load can dramatically impact sales and conversion.

Improved user experience

Since SPAs are so smooth and responsive, users tend to have a better experience browsing them. This is especially true on mobile devices, where waiting for a page to reload can be very frustrating. For example, the KeyCDN homepage allows you to search through blogs, scroll down, and find multiple pages worth of information without constantly loading new landing pages.

Ease of development

Developing a SPA is much simpler than creating a traditional website. With all the code loaded in one place, it's much easier to make changes and updates. You also don't need to worry about page load time or optimize your code for performance since that's all taken care of by the SPA framework.

The disadvantages of SPAs

Of course, nothing is perfect, and single-page applications come with their own set of disadvantages:

JavaScript dependency

The main problem with SPAs is that they require JavaScript to work. This means you need to make sure your website works for people who have disabled their browser's built-in support and those using a device without an up-to-date version of the language installed (for example, Android devices running older versions of Android).

Scalability and resilience

Since all of a SPA's functionality is contained in one page (and its sub-pages), it can be difficult to scale up or down as needed. If your website experiences a sudden surge in traffic, a SPA may not be able to handle the load and will crash. This is because SPAs rely on a limited number of servers to serve all their code, whereas MPAs can use any number of servers without affecting the user experience.

SEO optimization

Since optimizing progressive web applications is much more complex than normal multi-page apps because of their single-page architecture, MPAs often have better SEO optimization capabilities. This is because you can have multiple pages rank for keywords as opposed to one. This is especially important if you're using your website for marketing purposes and want to ensure that it appears in search engine results (and not just on social media).

Browser history

Since your actions in a SPA are all tracked on the same page, your browser's history will only show the last URL you visited. This can be confusing for users who are used to being able to revisit previous pages by clicking on the Back button.

When to use SPAs

In the end, whether you should use a SPA or not depends on your specific requirements. If speed and responsiveness are essential to your core business value proposition, it's definitely worth considering using a SPA as part of your marketing strategy. Suppose you're mainly concerned about user experience and ensuring that mobile users have a consistent experience across all your pages. In that case, a SPA framework might also be the right choice for you. It is also suitable for dynamic and interactive platforms that do not have high data volumes. These characteristics make SPAs an excellent choice for social networks, closed communities, and SaaS platforms. There are, however, many instances where an MPA would be better.

What is an MPA?

A multi-page application (MPA) is a website where each page is loaded independently instead of using a single-page application. Instead of all the code is loaded in one place, it's spread out across multiple pages. When picturing a multi-page application, imagine any website with multiple pages, such as Amazon or other online stores.

This approach has been around for much longer than SPAs and is still the most common way to build websites. It has several advantages, including:

Scalable and resilient code

Since each page is loaded on its own, it's easier to debug problems with an MPA. If the application crashes or experiences a bug of some sort, users can simply go back to previous pages without losing any data (the same cannot be said for SPAs). It also makes it easier to scale your website up or down as needed since you're not limited by the amount of code that can be loaded on a single page.

Easier for older browsers

Since MPAs don't rely on JavaScript, they are more compatible with older browsers that may not have the latest language updates installed. This is especially important if you have many users still using older browsers.

Browser history

Since an MPA doesn't rely on JavaScript, it also maintains browser history similarly to traditional websites. This means that users can revisit previous pages by clicking on the Back button, just like they're used to.

When to use MPAs instead

Although SPAs provide a much better user experience than MPAs, they're not always the best choice. MPAs work great for e-commerce sites, community sites, marketplaces, and business catalogs. They don't work well for social networks or websites that rely heavily on JavaScript.

Best practices in single-page applications

There are a few best practices that most SPA frameworks recommend:

Cache DOM elements

One of the best ways to improve performance is to cache DOM elements - that is, store them in a local database to be accessed quickly without reloading from the server. This can be done using libraries like React's own memory cache or Angular's $cacheFactory service.

Reduce network requests

Another way to speed up your application is to reduce the number of network requests it makes. You can do this by bundling files together, using caching, or loading only the necessary resources for a given page.

Use server-side rendering

If you're having trouble with performance on mobile devices, you can use server-side rendering to generate the initial HTML code for your application. This allows you to send pre-generated HTML pages to devices that don't have JavaScript enabled and also ensures better load times since the server can prep all content before sending it down.

Cache static pages

If you're using a SPA framework like Angular or React, there are ways to cache static elements of your website so they can be accessed quickly without having to load from the server. This is especially important for pages that don't often change, like your website's header and footer.

Use a CDN

Using a content delivery network (CDN) can also improve performance by caching static files closer to your users. KeyCDN, for example, offers edge servers around the world that can serve your files quickly and reduce latency.

The bottom line

Single-page applications are a great way to improve the user experience of your website. They offer many advantages over traditional multi-page applications, including faster load times, better compatibility with older browsers, and an improved user interface. However, they're not always the best choice for every type of website. When in doubt, it's best to consult a professional web developer to see which one is right for you.

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