10 Javascript Lazy Load Image Libraries

10 Javascript Lazy Load Image Libraries

The Intersection Observer is an API to conditionally perform some action when an element enters the viewport/view. So here are some Javascript lazy load image libraries that use Intersection Observer API to both maximize performance and user experience.

The Intersection Observer is an API to conditionally perform some action when an element enters the viewport/view. So here are some Javascript lazy load image libraries that use Intersection Observer API to both maximize performance and user experience.


yall.js is a featured-packed SEO-friendly lazy loader for img, picture, video and iframe elements, as well as CSS background images. It works in all modern browsers, including IE 11. It uses Intersection Observer where available, but as of version 3, this API must be polyfilled for older browsers. It can also monitor the DOM for changes using Mutation Observer to lazy load elements that have been appended to the DOM after initial load, which may be desirable for single page applications. It can also optimize use of browser idle time using requestIdleCallback, and reduce jank by using requestAnimationFrame.


gluebert.js is a tiny helper lazy loading DOM Elements, StyleSheets and JavaScript files using dynamic import and code splitting.

Accessible Image Lazy Load

It is a lightweight non-dependant javascript module that adds a different approach on lazy loading focusing on accessibility. Most existing options work by either making you drop the src attribute of the image or, making you create a base64 data / low resolution blurred alternative version of the image, or also including the img element into a noscript tag. This could be hacky and verbose and the main issue with it is that alters the semantics of the original element.


Highly performant, light 1kb and configurable lazy loader in pure JS with no dependencies for responsive images, iframes and more. It is written with an aim to lazy load images, iframes, ads, videos or any other element using the recently added Intersection Observer API with tremendous performance benefits. Existing lazy loading libraries hook up to the scroll event or use a periodic timer and call getBoundingClientRect on elements that need to be lazy loaded. This approach, however, is painfully slow as each call to getBoundingClientRect forces the browser to re-layout the entire page and will introduce considerable jank to your website. Making this more efficient and performant is what IntersectionObserver is designed for, and it’s landed in Chrome 51. IntersectionObservers let you know when an observed element enters or exits the browser’s viewport.


LazyLoad is a fast, lightweight and flexible script that speeds up your web application by loading your content images, videos and iframes only as they enter the viewport. It’s written in plain vanilla JavaScript, it leverages the IntersectionObserver API, it works with responsive images and it supports native lazy loading. Instead of listening to the scroll and resize events, LazyLoad uses the Intersection Observer API which is a new, blazing fast method to detect if an element is inside the browser viewport. Your users will see the difference in slow and even in fast devices or computers.

React Simple Img

React lazy load images with IntersectionObserver API and Priority Hints.

V Lazy Image

Lazy load images using Intersection Observer, apply progressive rendering and css animations. A Vue.js component to lazy load an image automatically when it enters the viewport using the Intersection Observer API.


Asynchronous boundary detection – lazy-loading, infinite scroll, and more. Whether you’re lazy-loading images, implementing infinite-scroll, or avoiding an ex-lover. it’s important to set boundaries. Historically, boundary detection required a mix of event handlers, loops, and calls to getBoundingClientRect. Since these operations run on the main thread, performance would suffer. Bounds.js defies these expectations, providing a simple and powerful API. It detects intersections between elements asynchronously, keeping complex operations off the main thread and improving performance.

Ng In Viewport

ng-in-viewport gives you a directive that uses Intersection Observer API. To provides a simple way to asynchronously observe changes in the intersection of a target element with an ancestor element or with a top-level document’s viewport.

Lazy Observer Load

A library to lazy load images using Intersection Observer.

Programming a Javascript Simon Game Tutorial

Programming a Javascript Simon Game Tutorial

In this javascript tutorial, I recorded myself live programming an html5 javascript simon game.

In this javascript tutorial, I recorded myself live programming an html5 javascript simon game.

For those who don't know, I'm a full stack web developer who has been in the industry for over 5 years now. There is a lot of things I have learned along the way and I'd like to share that knowledge with anyone wanting to learn!

like this video if you found it useful and would like to see more videos of the same content.

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Understanding Memoization And Dynamic Programming in Javascript

Understanding Memoization And Dynamic Programming in Javascript

In this Javascript tutorial I will explain what memoization is, how to use it, when you should use memoization, how to use memoization, what dynamic programming is, how to use memoization in dynamic programming. Memoization is a big complicated word that you may have never even heard before, but you may be surprised to know that you are most likely already using memoization without even realizing it.

Memoization is a big complicated word that you may have never even heard before, but you may be surprised to know that you are most likely already using memoization without even realizing it. Memoization is just the act of caching values so that they can be calculated quicker in the future. Memoization is really useful in all parts of programming, but where it is most useful is in dynamic programming. In this video I will explain what memoization is, how to use it, and why it is so useful especially in dynamic programming.

🧠 Concepts Covered:

  • What memoization is
  • When you should use memoization
  • How to use memoization
  • What dynamic programming is
  • How to use memoization in dynamic programming

JavaScript Programming Tutorial - Full JavaScript Course for Beginners

JavaScript Programming Tutorial - Full JavaScript Course for Beginners

JavaScript is the programming language of HTML and the Web. JavaScript is easy to learn. This tutorial will teach you JavaScript from basic to advanced. JavaScript Programming Tutorial - Full JavaScript Course for Beginners

Watch this JavaScript tutorial for beginners to learn JavaScript programming from scratch. 👍

⭐️Course Contents⭐️

01 | Introduction

Get an introduction from Bob, as he kicks off the course, sets expectations, and gives you a little guidance for the road ahead.

02 | Setting Up the Development Environment

See how to install Node and Visual Studio Code, and learn why you need each. Watch as Bob writes a first tiny line of code to make sure that the installation is ready.

03 | Basic JavaScript Syntax

Hear about the basics of the JavaScript syntax, including how JavaScript is executed, how to create a properly formed statement, and more.

04 | Variables

Learn what variables are and how to declare, initialize, set, and get values from them.

05 | Data Types

JavaScript works with data types differently than other programming languages do. Learn from Bob as he explains some of the most basic data types and how to determine the type held by a variable.

06 | Type Coercion and Conversion

Sometimes you need to explicitly convert the data type of a value into a different data type. Sometimes JavaScript will do this automatically for you. Bob explains how and why this happens.

07 | Expressions and Operators

Learn how to spot a well-formed expression and how to compose expressions through the combination of operators and operands.

08 | Arrays

Watch as Bob demonstrates how to use arrays, how to add/remove elements of an array, how to access elements of an array using the index, how to get the number of elements in an array, and more.

09 | Function Declaration

Get an introduction to functions, as Bob shows you one way to define a function, how to call the function, how to pass parameters into a function, how to return values from a function, and more.

10 | Function Expressions

Sometimes a function declaration is more than you need. Get details in this lesson, as Bob demonstrates how to use a function expression and how to create an immediately invoked function expression.

11 | Decision Statements

Learn how to add logic to your applications by testing conditions using if / else statements, switch / case statements, and the ternary operator.

12 | Iteration Statements

Watch as Bob introduces the For and While statements, which enable you to loop through lists of values and perform operations on them.

13 | Basics of Scope

Hear an explanation of the notion of the lifetime of variables and their reach into other code blocks, in this discussion of scope.

14 | Returning Functions from Functions

As a building block toward a more sophisticated approach to building JavaScript applications, see how you can return functions from functions.

15 | Object Literals

Objects contain properties and functions that describe attributes of the object and its behavior, respectively. Watch as Bob demonstrates how to create object literals.

16 | Module Pattern and Revealing Module Pattern

Learn how to introduce variables and functions without leaving an unnecessarily large footprint on the global scope.

17 | Closures

Closures allow developers to bind functions to their execution context, including variables, so you can build specialized versions of functions. Learn how closures work and how to create them.

18 | this Keyword

Get the details on the "this" keyword, which causes a lot of confusion for JavaScript developers. Listen as Bob explains what this mysterious object is and how to bend it to your will.

19 | Destructuring

See how to use destructuring, a new feature in JavaScript that allows you to unpack array elements or object properties in a concise syntax.

20 | String Template Literals

Learn about the new string template literal syntax to enable string interpolation, multi-line string formatting, and more.

21 | Regular Expressions

Working with string data, Bob explains how use regular expressions to determine such things as whether a string matches a specific pattern or whether an instance of the pattern exists in a string.

22 | Built-In Natives

Join Bob as he examines native, built-in JavaScript functions that return objects that box the primitive types in order to provide additional helper methods on your values.

23 | Constructor Function Calls with the new Keyword

Learn how constructor functions work, see how to make key distinctions in what they are, and find out why they’re helpful.

24 | Objects and the Prototype Chain

Moving past the absolute beginner matter, listen in as Bob explains how objects work in JavaScript and how you can create an object that is linked to another object.

25 | JavaScript Classes

Bob demonstrates how “syntactic sugar” works on top of the existing functions and prototype chaining to help JavaScript resemble more traditional object-oriented programming languages.

26 | Arrow Functions

The latest version of JavaScript added arrow functions, a shorthand syntax for creating functions. Watch as Bob demonstrates how to create them and shows where they’re useful.

27 | Truthy and Falsy Values

Listen is as Bob circles back to topics that are important (but didn’t easily fit into earlier topics) and looks at the odd way in which JavaScript evaluates certain expressions as truthy and falsy.

28 | null Type

Similar to the undefined primitive type, the null type represents a variable that has no reference to an object when one was expected. Hear an explanation of how and why we should think about nulls.

29 | Date Objects

No discussion of JavaScript would be complete without understanding the Date built-in native function which provides properties and methods for working with dates and times.

30 | String Methods

The built-in native String function provides several very useful methods for manipulating and evaluating strings. Watch Bob demonstrate how to use a few of the most useful ones.

31 | Array Methods

We’ve worked with arrays throughout this course. Now Bob takes a few minutes to show you some of the most useful methods provided by the Array built-in native function.

32 | Error Handling with Try Catch

See how to wrap a try/catch/finally statement around potentially problematic code to anticipate everything that could go wrong with it, and learn other error-handling tips.

33 | Understanding the Document Object Model

Watch Bob examine the web browser environment and how it creates an object graph of nodes that represent elements, their attributes, and text, plus how to properly attach your code to an HTML page.

34 | Working with DOM Nodes

Continuing from the previous video, Bob demonstrates a slightly more compelling example that helps us understand how to manipulate, create, and delete element nodes and attribute nodes.

35 | Course Conclusion

In this final video, Bob briefly adds some closing comments and well wishes. You can also optionally complete a survey to provide insight into how Microsoft can improve this course.

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