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Web Dev

Lazy Loading

With lazy loading logic in place, we no longer load resources without making sure that they are really required.

Load media on a web page only when the need be

Table of contents
  1. (Easy)
  2. Units
  3. Chapters
  4. Quizzes
  5. Exercises
  6. Projects
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Things to know

What is this course about?

Lazy loading is a technique for loading images on the web only when they are needed to. It uses the idea of an image's appearance into the viewport which drives a procedure to load the image into view. Lazy loading is employed extensively around the web.

Most blogs, image galleries, and websites of other niches, use it to decrease loading times and save their user's device and network resources, such as battery and cellular data. Without lazy loading they will be left to simply eagerly load the images in the HTML which will in turn affect their sites' loading times, and ultimately their user base.

Not only does lazy loading improve the loading times of web pages but also makes sure that they look professional, elegant and leave an impression to the user that the developers of the site have put in at least some effort to design it. Lazy loading is so common out there that if you're about to start up a blog it will show in the suggestions for you to do. So why not start learning it today?

What will you learn in this course?

In this course you'll learn:

  1. How to incorporate HTML, CSS and JavaScript into building something useful for the web. You'll get to know how to build any application or utility for the web by first laying out its structure in the HTML and CSS, then thinking through how will elements interact with each other and then finally laying out the JavaScript code to blend all it together.
  2. What are responsive images in CSS and how in this modern era of designing developers are required to know these concepts to make their web applications be mobile-friendly.

Why should you take this course?

There have to be reasons for you to take this course, right? After all, time is precious, isn't it? And definitely there are a couple of reasons to learn lazy loading.

  1. Firstly you'll learn a popular technique used all around the web, not only in its name but also in its internal workings. You'll get to know exactly how all those complex algorthms out there, to lazy load images, work at the most basic level.
  2. Secondly you'll refine further in your skills of JavaScript by solving various problems arising throughout this tutorial. You'll get to discover how to implement fade effects, error handling, function closures and much more in JavaScript in this very tutorial.


  1. HTML

  2. CSS

  3. JavaScript

Table of contents


In this single unit we'll consider all that we need to know to implement a perfect and fully-functional lazy loading algorithm. We'll see how to calculate element offsets; how to track scroll positions; how to give fade effects to the images as they load; how to handler any errors creeping into the program and much more on this road.

Let's begin learning.

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