The world would be so chaotic if we had to be aware of everything computers do for us. That is why most software applications need to perform their tasks with very little user input; in fact, users should only be aware of how your app is functioning if there is an absolute need for them to know.

Abstraction is so important in technology, which is why JavaScript provides different web APIs that help you build applications that do what they need to do with minimal user input while maintaining synchronized interaction with the necessary parts and networks. In this article, you will learn about the APIs, what each of them does, and how to start using them in your applications.

Prerequisites

The primary prerequisite to follow along with this article is to be familiar with the basics of JavaScript. Also, it'll be beneficial if you read the introduction of the series.

Now that the introduction and prerequisites are out of the way let's explore the JavaScript Web APIs under the Background and Synchronization category in the following sections.

Background Fetch API

The Background Fetch API is an experimental API that helps your application manage downloads that take time to complete without the need to stay on the application, keep it open, or keep the internet connection open forever. It detects the different states of your device and connectivity to pause, resume, or even stop the download.

Let's explore some of the things you can build with this API in the following sections.

Offline Content Caching

The Background Fetch API can be used to download and cache content in the background while the user is actively using the application. This can be particularly useful for apps that require frequent updates or content synchronization, such as news or social media apps. The API allows you to prioritize and manage the download process, ensuring a seamless offline experience for users.

Batch Data Synchronization

The Background Fetch API can be leveraged to perform periodic batch data synchronization between a client-side application and a server. For example, a productivity app could use the API to sync data like tasks, notes, or calendar events in the background at regular intervals. This improves the app's responsiveness and reduces the need for manual synchronization, providing users with up-to-date information even when they are not actively using it.

Background Asset Preloading

The API can be utilized to preload or cache significant media assets, such as images, videos, or audio files, in the background while browsing a website or using a web app. By proactively fetching and storing these assets, the API enhances the overall user experience by reducing load times and enabling smoother transitions between different sections or pages within the app.

Now that you know how to use this API to improve your applications let's see what you need to know to start implementing it in the next section.

Background Fetch API Implementation

The Background Fetch API is still in active development at the time of writing. However, according to its browser compatibility chart, it supports over 50% of major web browsers.

That said, the implementation is pretty straightforward as it uses only 5 main interfaces, has a very descriptive video from its developers at Google, straightforward examples on its usage and detailed specifications on its MDN page.

Background Sync API

The Background Sync API is an experimental API that enables developers to defer user tasks to a service worker so it can be handled whenever the user has a stable internet. Let's explore some of its use cases in the following sections.

Reliable Offline Data Submission

The Background Sync API enables web applications to queue data submissions when the user is offline and automatically synchronize them when the network connection is restored. This can be valuable in scenarios where users need to submit forms, upload files, or interact with server-side resources, even in an offline or low-connectivity environment. The API ensures that critical data is not lost and provides a seamless experience for users, eliminating frustration caused by network interruptions.

Real-time Collaboration

Web-based collaborative applications, such as document editors or project management tools, can leverage the Background Sync API to keep data in sync across multiple devices and users. Changes made by one user can be stored locally and synchronized in the background when the connection is available. This allows for smooth and uninterrupted collaboration, even with network disruptions or intermittent connectivity.

Background Notifications and Updates

The API can be utilized to deliver background notifications and updates to users. For example, a messaging application can use the Background Sync API to fetch new messages in the background and display notifications to users even when they are not actively using the app. This keeps users informed and engaged, ensuring they get all important messages and updates.

Background Sync API Implementation

It is important to note that the Background Sync API is only available in Progressive Web Apps at the time of writing. However, it supports more than 40% of major web browsers, so you might need to refer to the browser compatibility chart before implementing it in your apps.

Its implementation is relatively straightforward because it uses only two interfaces under the hood and you can see examples of implementation, its specifications, and more details on its MDN page.

Background Tasks API

The Background Tasks API enables developers to manage the execution of tasks based on their importance. It allows you to determine which tasks should be executed as soon as possible and which can run when the application is idle. Let's explore some of the things you can use this API for in the following sections.

Periodic Data Synchronization

Background Tasks API can be used to periodically synchronize data between a web application and a server. For instance, an email client could schedule a background task to check for new messages at regular intervals, ensuring that the user's inbox remains up to date without requiring manual refreshes. This improves the user experience by providing timely information and reducing the need for manual interaction.

Background Data Processing

Web applications often need to perform computationally intensive tasks or data processing operations. The Background Tasks API can be employed to execute these tasks in the background, preventing the user interface from becoming unresponsive or slowing down. For example, an image processing application could use a background task to apply complex filters or manipulate large images without blocking the user's interaction with the app.

Scheduled Notifications and Reminders

Background Tasks API can be utilized to schedule and deliver notifications or reminders to users. For instance, a task management app could schedule a background task to send reminders for upcoming tasks or events at specified times. This ensures that users receive timely notifications even if they are not actively using the app, helping them stay organized and on top of their commitments.

Background Tasks API Implementation

The Background Tasks API is a mature API that supports over 80% of the major web browsers. You might also want to explore some of the motivations behind its development.

Its implementation is relatively straightforward as it only uses a single interface under the hood and there are examples, specifications, and other details that you can reference when implementing the API on its MDN page.

Push API

The Push API enables you to build applications that can receive messages from the server without the need to be online or loaded, which ensures that your users get updates and notifications promptly. Let's explore some of the things you can do with this API.

Real-time Notifications

The Push API enables web applications to send push notifications to users' devices even when they are not actively using the application. This is beneficial for various applications such as messaging platforms, social media platforms, or news apps, where real-time updates are crucial. By utilizing the Push API, applications can deliver essential notifications, messages, or alerts directly to users' devices, enhancing user engagement and keeping them informed.

Personalized Content Delivery

With the Push API, web applications can deliver personalized content based on user preferences or behavior. For example, an e-commerce platform can send push notifications about personalized product recommendations, exclusive deals, or price drop alerts. By leveraging user data and the Push API, applications can provide targeted and relevant content, increasing user engagement and conversion rates.

Background Data Sync

The Push API can be used to trigger background data synchronization between a web application and a user's device. For instance, a note-taking application can use push notifications to inform users about updates made on other devices and automatically sync the changes in the background. This ensures that users have access to the latest version of their data across multiple devices, providing a seamless and synchronized experience.

Push API Implementation

The Push API is a mature API that supports over 90% of the major web browsers.

Its MDN page explores its concepts and usage deeply for people who need deep technical details of the API, its interfaces, examples, specifications, and a detailed browser compatibility chart.

Service Workers API

The Service Workers API is usually used as a proxy between applications and their servers. The motivation behind its creation is to enable applications to keep working effectively, even with little or no internet connectivity.

The Service Workers API can be described as the significant backbone behind the previous APIs we've explored in this article, as it powers most of them behind the scenes in one way or the other. Let's explore some of the things this API helps you achieve in the following sections.

Offline Capabilities

The Service Workers API enables web applications to work offline by caching essential assets and providing offline functionality. For example, a news application using service workers can cache news articles, images, and other resources, allowing users to access previously visited articles even without an internet connection. This improves user experience and ensures that content remains accessible even in offline or low-connectivity environments.

Background Content Updates

Service workers can be used to perform background content updates for web applications. For instance, a weather application can use a service worker to periodically fetch the latest weather data in the background and update the user interface with the most current information. This ensures that users always have the most up-to-date data without requiring them to refresh the page manually.

Push Notifications

The Service Workers API plays a crucial role in enabling push notifications. Service workers act as event-driven background processes that receive push notification messages and display them to users, even if the application is not currently open. This allows web applications to deliver timely and relevant notifications, such as new messages, reminders, or social media updates, enhancing user engagement and interaction.

Note: The Service Workers cannot implement most of these use cases by itself and needs to be combined with one or more of the previous APIs to do an excellent job.

Service Workers API Implementation

The Service Workers API uses a lot of interfaces under the hood, and you can see its specifications, concepts and usage, use case ideas, and much more on its MDN page.

Conclusion

And that's it! I'm sure you learned something new, no matter your level of experience using JavaScript to build web applications.

In this part of the series, you learned about the JavaScript web APIs that enable you to build compelling applications that work with little to no interruptions due to the unavailability of internet connections and the cool features you can build using them. You also explored how to implement them and the information you need to know through the linked resources in the implementation section of each API.

Finally, remember to follow me here on Dev and Twitter. Thanks again for reading, and I'll see you in the next one! 👍