Book Image

Progressive Web Application Development by Example

By : Chris Love
Book Image

Progressive Web Application Development by Example

By: Chris Love

Overview of this book

Are you a developer that wants to create truly cross-platform user experiences with a minimal footprint, free of store restrictions and features customers want? Then you need to get to grips with Progressive Web Applications (PWAs), a perfect amalgamation of web and mobile applications with a blazing-fast response time. Progressive Web Application Development by Example helps you explore concepts of the PWA development by enabling you to develop three projects, starting with a 2048 game. In this game, you will review parts of a web manifest file and understand how a browser uses properties to define the home screen experience. You will then move on to learning how to develop and use a podcast client and be introduced to service workers. The application will demonstrate how service workers are registered and updated. In addition to this, you will review a caching API so that you have a firm understanding of how to use the cache within a service worker, and you'll discover core caching strategies and how to code them within a service worker. Finally, you will study how to build a tickets application, wherein you’ll apply advanced service worker techniques, such as cache invalidation. Also, you'll learn about tools you can use to validate your applications and scaffold them for quality and consistency. By the end of the book, you will have walked through browser developer tools, node modules, and online tools for creating high-quality PWAs.
Table of Contents (12 chapters)

Lazy loading images

Images can delay your overall page load experience due to image numbers and their size. There are different strategies for optimizing image delivery. The first one you should consider is lazy loading images below the fold.

This could be a very tricky technique to execute. Modern APIs can help you, the IntersectionObserver (https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API) API in particular gives you the ability to detect when elements are entering the viewport. You can designate the distance and time estimated threshold for an element to appear.

The IntersectionObserver API will trigger an event to let you know when an element is about to be displayed. At this point, you can initiate an image download if necessary. This means that your pages images will not be loaded in the initial render process, but be loaded as needed. This can...