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10 things you need to know about SPA (Single Page Application)
September 17, 2021 | Learn programming

SPA is an abbreviation that stands for Single Page Application. First of all, you’re most likely a regular user of Single Page Applications already – you’ve met them through Gmail, Pinterest, PayPal and even Netflix. This article will teach you everything you need to know about SPAs – what is a single page application, what are the main benefits of SPA and what advantages does it bring to users and businesses. We will also learn how does SPA work with SEO, and what are its main pros and cons.

What is a Single Page Application (SPA)?

A single-page application is an app that works inside a browser and does not need to reload the page during its work.
You are using SPAs every day, Gmail, Google Maps, or Twitter for instance. All these SPAs are all about imitating the natural browser environment – they aim for no page reloads and no waiting time for the end-user. User experience (UX) is the ultimate goal – SPAs keep the user in one, comfortable web space where he consumes content in a simple and easy way – so, it is just one web page that loads all other content using JavaScript after your visit. In other words, SPA requests the markup and data independently and then renders pages straight in the browser.

What are the main advantages of SPAs?

1. Speed is one of the main advantages of SPAs.

Most resources, such as HTML, CSS, and scripts are loaded only once through the lifespan of an app, and then during the use of the application, only data is transmitted back and forth. Data that is transmitted to and from the server is the only thing that changes, so it is also the only thing that needs to be “updated” when the user users the app. All the other sources that the app needs are loaded at the launch of the app and they don’t need to be reloaded when the user again uses the app. Consequently, the application is very responsive to the user’s requests and doesn’t have to wait for client-server communication all the time.

2. The process of developing SPA is optimized.

Developers don’t need to write code to render the pages on the server. Even more, they don’t even really need a server to begin the development process. They can start the development from a file file://URI to get started. In addition, the developer can completely reuse the same backend server-side code and efficient API for the web application and a native mobile app. The development of SPAs works out nicely when you have a team of developers working together – for example, backend developers pay attention on the API, and the frontend developers focus on the creation of the best user experience.

3. SPAs work effectively with local storage.

The caching process is very efficient – SPA sends one request, stores all data and then it can use cached data and can even work offline. So, SPAs work effectively with local storage and this might come in handy at times when the user has poor connectivity.

4. The process of debugging SPAs is straightforward.

Debugging is done through Chrome by using a console, where you monitor operations and investigate page elements and data that are associated with it.

What are the main disadvantages of SPAs?

1. SPAs are less secure.

This is especially the case if we compare SPAs to the “traditional” applications. Because of the cross-site scripting (XSS) and the fact that no new pages are loaded, attackers can inject client-side scripts into web applications.

2. SPAs can be slow to download because client frameworks that are required to be loaded to the client are heavy.

The main advantage of SPAs is their speed, but on the other hand, SPAs also put a more significant load on the browser. For example, if your users have devices with low power, they will also have a poor experience with your app in terms of speed.

3. Does your SPA consume more memory than it needs?

That is one thing you need to make sure it’s fixed – you need to make sure there are no memory leaks. The thing is that the app can run for hours at a time, so you need to make sure your SPA doesn’t consume more memory than it needs. If it does, users’ positive experience with fast loading pages will be destroyed because they might have problems with available memory on their devices and the app might become slower.

4. Does the user have JavaScript enabled?

SPAs require JavaScript to be enabled in the browser, it simply cannot work without it, so the users should not have JavaScript disabled on their devices. If they do, then you need to think of additional ways of how they can access the information on your website or your app without JavaScript. You could solve this problem if you render the page on the server-side aka isomorphic rendering, theoretically, you would get a rendered page although the user has disabled JavaScript.

5. The privacy of sensitive data.

This is another security issue. The entire SPA loads right away to the user’s device, which means you might accidentally give away data that should not be available at all, or at least hidden behind the user’s login. For this reason, the initial page load should not contain any information that shouldn’t be visible to all users. Make sure to implement that.

6. What about SEO (Search Engine Optimization)?

Search engine optimization is probably one of the main disadvantages of SPA use. With SPAs the URL doesn’t really change, and different pages don’t usually have their URL addresses, so the SEO part of SPAs can be tricky. Compared to the traditional server-rendered pages, it is harder for search engines to index your SPA website. SPA content is loaded by AJAX, which is a method of exchanging data and updating that data in the application without refreshing the page. However, nowadays data exchange can be done on a server-side as well, which makes SEO for SPAs easier. So, if you don’t want to bother with the URL settings, choose a framework that supports server-side rendering (SSR). You should also pay special attention to the server messages, especially the 200 and 404 errors. In addition, you need to use static URLs, and optimize the scripts on your page to speed them up. Obviously, make sure your pages have HTML5 for Google crawlers to be able to access them.
At the end of the day, it is safer to use SPAs when you don’t rely on SEO as much or if your app can only be accessed via a login.

So, what is the main advantage of SPAs for end-users and businesses?

The speed at which the app loads and the ability to work offline are definitely some of the main advantages of SPAs for end-users. Another advantage is usually how easy the application is for the usage – the navigation and where to find this or that are more or less intuitive. SPAs also work great in the mobile environment too because most of the time all the user needs to do is scroll.
When it comes to the benefits of SPA for businesses, the development of SPAs usually takes less time and is much easier to create a standalone native mobile application. The main reason for this lies in the fact that the same backend API can be used for both web and mobile application. In addition, as said above SPAs are faster for the end-user which is obviously a benefit for the business too.

SPAs – How do they work?

Single-page application architecture consists of the client-side technologies (React.js, Angular, etc.) and the server-side technologies (for example Node.js). In terms of the way the site renders as it is presented to the user, there are three options to choose from:

Client-side rendering might be the best option for simple websites. The downside is that rendering the information on the client-side requires a lot of resources from the device and might overload the browser. Consequently, this option might be the slowest of the three. On the other hand, if your website has good traffic, client-side rendering is the best option because it can present the information to the user without having to communicate with the server too much – it economizes with the server’s resources.
Server-side rending uses server resources more, but it also covers the downsides of client-rendering, because it combines both the speed of the single-page application and doesn’t overload the user’s browser, which makes the app fast.
Static site generators are a fast option, but they are oriented more at static pages. So, if your website’s main component is dynamic content, static site generators aren’t the best answers.