Lazy Loading and All You Need to Know

Lazy Loading and All You Need to Know article image

Lazy loading is a modern web implementation that provides dynamic loading of contents without reloading the page. This relies on special code that needs to be inserted in the web pages and then be correctly read and applied from the visitors’ web browsers. This article will give an overview of how it works and its benefits.

What is Lazy Loading and How It Can Be Implemented in Website Building?

Lazy loading is a standard web design practice based on a programming pattern that follows a simple approach: an object will get loaded only when needed. In website building terms, it is also called asynchronous loading, which means that website contents and elements will be loaded on a need basis without refreshing the page.

This mechanism is primarily used for images at two main points: after above-the-fold content is loaded or certain conditions are met. This also provides a performance relief of the servers. This is proven by the fact that if the page is not scrolled all the to the bottom, any images placed in the end will not be loaded.

This will save not only bandwidth (which can be expensive for high-traffic sites), but also spare the web browsers speed. According to web developers, there are several approaches which can be undertaken by the web developers:

  • Code splitting — This relies on the developers to split the code pieces that apply to different technologies: JavaScript, CSS, and HTML. By splitting the overall into smaller parts and linking it in different objects and resources. Minimal code will be sent to the web browsers, which will significantly improve page processing time.
  • JavaScript Optimization — JavaScript codes can be deferred by treating the scripts as modules. This is done by applying the type=”module” declaration.
  • CSS Code Optimization — CSS resources are considered as render-blocking resources meaning that the processed contents will be loaded only when the valid sheets are loaded. A possible way will be to link the CSS files to separate files.
  • Fonts Optimization — Delayed text rendering is the result of font requests that are delayed until the render tree is constructed. This can be overridden by using CSS.

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How To Implement Images Lazy Loading in Websites?

Using it for images has several advantages, especially when the site is build using a complex CMS system like WordPress or Joomla. They typically implement JavaScript code that is programmed to display contents using DOM objects as containers. In most implementations, the scripts that are part of a given site will wait until the DOM has executed. Images that load asynchronously can make a heavy impact on thebounce rate — the ratio of users leaving the site due to heavy load and those that continue to browse.

Last year native specification was implemented in all major web browsers for both desktop and mobile users. This means that web developers can implement such a specification for images using the tag. This can significantly reduce web page loading time because images are the most requested asset type. This means that if images are inserted using this approach website, visitors can load the pages much faster. At the same time, the website operators will significantly reduce their bandwidth requests.

While this method may be popular with most web developers, some software may not correctly read the tags and confront the designated behavior in some circumstances. In such cases, there can be other solutions that provide a better approach. A modern approach is the use of the Inersection Observer API. This is a web development mechanism that will asynchronously observe changes in the changes (intersection) of a given element compared to an ancestor element or a top-level document’s viewport. In a nutshell, it leverages lazy loading to various types of web content, including images. The typical scenarios used by this API are the following:

  • Images and other content can be programmed to load as the visitors scroll down a given page
  • The implementation of infinite scrolling in content-heavy pages
  • Banner tracking and advertising reporting for ad revenue calculation
  • Decisions of animating processes based on the visibility to the visitors

Another method that web developers can use is to utilize the Lozad.js JS library. This is a performance-optimized, light, and easy-to-use lazy loader that has no dependencies. This means that no additional jQuery code is required in order to implement it in sites fully.

Developers will need to be careful and test the code in complex situations for any bugs. A wrong code can lead to hibernate pages that will not display correctly. We at will continue to monitor the web development trends and provide useful content to our readers.

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