What are single-page apps and progressive web apps?
Single Page Applications (SPA) and Progressive Web Applications (PWA) are revolutionizing the web. These are two new technologies that look alike, but are not. Opposite, people often use them interchangeably.
Let’s take a look at the basic features and architecture of each of them to better understand them.
What are single page apps?
SPAs, so to speak, are websites that dynamically load content onto a single page. Essentially, every form of content and item you need to interact with spans a single page. This means that you don’t need to load separate Document Object Models (DOM) when browsing such a website.
That said, the goal is to keep users on the same page by loading everything they need to use and view at the same time. This translates into a better user experience.
The user interface, on the other hand, depends on how you design and organize your SPA. It boils down to why you might want to split the stretched page into navigations. And that doesn’t prevent it from being a single page, as the content always loads only once.
So when you browse a SPA, you are browsing preloaded content in a single DOM and not visiting different DOMs as you might have mistakenly believed.
Because it imparts speed, most business applications have embraced the idea of turning their websites into one page. Netflix, YouTube, PayPal, Facebook, Instagram, Twitter, and Pinterest are all examples of SPA.
What are progressive web apps?
A PWA is a web application or software that uses standard and emerging web browser guidelines in its functionality. PWAs, unlike SPAs, base their architecture on a set of guidelines that make them scalable, user-adaptable, lightning-fast, installable, and native-style.
Introduced in 2015 by Google, the goal of a PWA is to create applications that speak directly and gradually to its users. It aims to allow users to continue using the app even with poor or no network connection.
Invariably, a PWA provides everything you need in the blink of an eye. It does not go through the typical initial content load characteristic of a SPA.
Therefore, a user then interacts with the application as if it were native. While an essential feature of PWAs is their installability, you can still access them on the fly through your web browser without any installation. That said, like any other website, a PWA must also have a URL.
Progressive web apps are unique in that they have background wizards that deliver content in the blink of an eye. So even before accessing the web application, the content and components are readily available for your use. This makes them super fast and more reliable.
Apps like Spotify, Slack, and Uber, among others, are examples of PWAs.
PWAs generally have a common architectural rule. In order for a PWA to work as it should, it must have the following attributes:
1. A worker
Service technicians easily deliver content in PWAs. They ensure that your application can load relevant cached data when there is no network connection. This is possible using the Cache API, which stores responses to your requests offline. Thus, a worker interferes with browsing and user requests.
Using a promise object, a worker can provide already downloaded content if requested by a user (even when offline). A service worker, however, grants a non-blocking property to PWAs.
2. A secure context
A service worker needs a secure connection (HTTPS) for the confidentiality of the content delivered. When you send a request, a worker establishes secure communication between the PWA and the browser. A secure context therefore prevents privacy breaches such as a man-in-the-middle attack (MITM) in PWAs.
3. A web application manifest file
A web manifest is a JSON file that defines the characteristics of a PWA. It details the prerequisites for accessing, discovering and using the content of a PWA. It usually includes the name of your app, its URL, and its components. Ultimately, a manifest file contains the information needed to turn your web application into an installable application.
What are the similarities between PWAs and SPAs?
While the background logic of PWAs and SPAs is different, they only share a few things in common. While their delivery speed can differ significantly, conventional websites still lag behind in terms of speed and accessibility.
They both aim to improve the user experience by providing a responsive interface.
Because they both offer an app experience, it’s easy to mix them up, and you can barely tell which is which when you interact with them. Finally, on that note, both need a URL before they can be accessed.
The main differences between SPAs and PWAs
PWAs and SPAs may share some notable characteristics in common, but they are two different things. Here are the main feature differences you should note:
Main characteristics of single page applications
They are only accessible through the browser.
Although not recommended, you can serve them over an unsecured network (HTTP).
They don’t need service staff.
SPAs do not have a JSON manifest file, which means they are uninstallable.
They should be one page.
Not accessible when there is no network.
Main features of progressive web apps
Accessing them through the browser is an option as they are installable.
All PWAs need service technicians and must make requests over a secure network (HTTPS).
Responses are cached and delivered via a promise object.
They are accessible even without a network connection.
They are faster than SPAs.
They always have a manifest file, so they are downloadable, installable, and easily accessible.
A PWA cannot be a single page application.
SPAs and PWAs influence website delivery
With many corporate websites now embracing these new technologies, there is now a positive shift towards their service delivery.
More importantly, adopting PWAs improves the overall user experience, which in turn reduces bounce rates and increases revenue for most business applications. SPAs, on the other hand, have also rejuvenated social media, making it easy for people to interact on the web without slow page loading.
Should you use synchronous or asynchronous programming for your next project? Find out here.
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