Lazy load w3school

Christian Holst is the co-founder of Baymard Institute where he writes bi-weekly articles with their research findings on web usability and e-commerce … More about Christian Holst ….

Every second Tuesday, we send a newsletter with useful techniques on front-end and UX. We tested among other things these three design patterns for loading products, both on desktop and mobile. Pagination is still the most popular way to load new items on a website because it ships by default in almost every single e-commerce platform. We found that infinite scrolling can be downright harmful to usability — in particular, for search results and on mobile.

Throughout our large-scale usability study of e-commerce product lists and filteringnumerous test subjects explicitly complained about pagination. Test subjects generally perceived pagination to be slow, and the presence of more than a handful of pagination links would often discourage them from browsing the product list.

On the upside, they spent relatively more time on the first page of results. With infinite scrollingsometimes referred to endless scrolling, the user largely experiences the page as if all products are loaded at once regardless of whether they actually see all of the productsbut without the performance penalty of potentially hundreds of products loading.

Therefore, when infinite scrolling is implemented well, it can make for an incredibly smooth and seamless experience. The user can just scroll the list of products without any interruption. No interaction is needed — products simply appear as the user scrolls down the page.

However, initial results received relatively less exposure. This is one of the major design challenges of infinite scrolling: Because results continually load as the user approaches the bottom of the list, the user will see the footer for a second or two until the next set of results is loaded and suddenly inserted, pushing the footer out of view. If many items are in the list which is often the case with search and high-level categoriesthis effectively prevents the user from ever reaching the footer.

This can be highly problematic because the footer often holds links to vital help pages, cross-navigation, inspirational category content, and information about customer support, shipping, and returns.

Having one consolidated list of goods made it significantly easier for users to evaluate which products would be the best to navigate to and, consequently, increased the overall product discoverability rate. So, which loading method should you use? Note: These findings are from testing e-commerce websites.

lazy load w3school

Performance might vary on other types of websites. Note that the number of products to load is purposely a range here. For lists with more spec-driven products most consumer electronics, hardware, parts and suppliesuse the lower range. In contrast, testing showed that users can deal with a higher number of items when the list contains more visual products apparel, furniture, decor, etc. This way, pages load quickly because very few products are loaded initially.

More importantly, for small and medium-sized categories, lazy-loading will let the user browse the breadth of products without interruption. The new items will then be appended to the list, and the footer will be pushed down and the scroll bar extended.

During testing, this resulted in a jagged page experience. This faux page height will give the scroll bar the appropriate space from the beginning and, therefore, is a more accurate representation of the actual height of the list. It also gives the user access to the footer without any jumps whatsoever. And lazy-loading will continue to load products as before — only now they are taking up the empty space instead of extending the page.

Due to the open-ended-ness of search, it tends to have far more results than category browsing.

Create a Responsive Website With the W3 CSS Framework

In our usability study on e-commerce searchhundreds of search results were not an uncommon sight, and on mass merchant websites, search queries often return thousands of results.

Furthermore, with search, results are sorted by relevance.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. Lazy Load delays loading of images in long web pages. Images outside of viewport will not be loaded before user scrolls to them.

This is opposite of image preloading. This is a modern vanilla JavaScript version of the original Lazy Load plugin. New version loans heavily from a blog post by Dean Hume.

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By default Lazy Load assumes the URL of the original high resolution image can be found in data-src attribute. You can also include an optional low resolution placeholder in the src attribute. With the HTML in place you can then initialize the plugin using the factory method. If you do not pass any settings or image elements it will lazyload all images with class lazyload. If you prefer you can explicitly pass the image elements to the factory. Use this for example if you use different class name.

Note that destroy does not load the out of viewport images. If you also want to load the images use loadAndDestroy. If you use jQuery there is a wrapper which you can use with the familiar old syntax. Note that to provide BC it uses data-original by default. This should be a drop in replacement for the previous version of the plugin.

Low resolution placeholder ie. You can see this in action in this blog entry. Scroll down to see blur up images. Lazyloaded Responsive images are supported via data-srcset. If browser does not support srcset and there is no polyfill the image from data-src will be shown. All code licensed under the MIT License.

All images licensed under Creative Commons Attribution 3. In other words you are basically free to do whatever you want. Just don't remove my name from the source. Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

Sign up. JavaScript Makefile. JavaScript Branch: 2. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again. Latest commit.Learn Development at Frontend Masters. Use a blank. Frontend Masters is the best place to get it. Check it out. Same here on iPad 3 — nothing happens, no fallback to see, even with the last updated version Feb 23, …. I know this is out of date, but I had this problem too. On touch devices it waits until after the scroll has completed, which on iPhone means an empty image for a few seconds while it slowly stops.

The way I fixed it, with the suggestion from Matt, was to add. Chris, what happens to no-js users? Anselm: iPad is not a no-js user.

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Especially regarding images. You could also add a function which parses the DOM to create the data-source after the page is loaded which replaces the src attribute dynamically.

Hi Vincent! Does this plugin work with background-image property instead of using tags? Thank you! To make images load slower than they should? If a user clicks through your pages, why would you waste bandwidth on that photo at the bottom of your post, when the user never scrolled there to view it? On a high traffic site, say 2 million of 5 million users visit a blog post with a lot of images on it, but never scroll down.

Below the fold, there is k of images. Lazy Loading images is for postponing loading of images outside the browser viewport. The idea is that those images does not need to take up bandwidth until just before they are needed, making room for other resources to be loaded faster.

I like how in that one, the img tags use the real src attributes like normal. Unfortunately, this seems to defeat the whole purpose of lazy loading. Looking at a network inspector, I saw every image loaded when the page loads, and loaded a second time when scrolling down.

It would be great if we could get the best of both worlds — ordinary markup and real lazy image loading — but I have doubts about it being possible. Using real src attributes basically guarantees the images will start loading before JS can intervene.The portion of images and video in the typical payload of a website can be significant.

Unfortunately, project stakeholders may be unwilling to cut any media resources from their existing applications. Such impasses are frustrating, especially when all parties involved want to improve site performance, but can't agree on how to get there.

Fortunately, lazy loading is a solution that lowers initial page payload and load time, but doesn't skimp on content. Lazy loading is technique that defers loading of non-critical resources at page load time.

Instead, these non-critical resources are loaded at the moment of need. Where images are concerned, "non-critical" is often synonymous with "off-screen". If you've used Lighthouse and examined some opportunities for improvement, you may have seen some guidance in this realm in the form of the Offscreen Images audit :. An example of image lazy loading can be found on the popular publishing platform Mediumwhich loads lightweight placeholder images at page load, and replaces them with lazily-loaded images as they're scrolled into the viewport.

If you're unfamiliar with lazy loading, you might be wondering just how useful the technique is, and what its benefits are. Read on to find out! Because it's possible you're loading stuff the user may never see.

This is problematic for a couple reasons:. When we lazy load images and video, we reduce initial page load time, initial page weight, and system resource usage, all of which have positive impacts on performance. In this guide, we'll cover some techniques and offer guidance for lazy loading images and video, as well as a short list of some commonly used libraries.

Image lazy loading mechanisms are simple in theory, but the details are actually a bit finicky. Plus there are a couple of distinct use cases that can both benefit from lazy loading. Let's first start with lazy loading inline images in HTML.

If they are, their src and sometimes srcset attributes are populated with URLs to the desired image content.

lazy load w3school

If you've written lazy loading code before, you may have accomplished your task by using event handlers such as scroll or resize. While this approach is the most compatible across browsers, modern browsers offer a more performant and efficient way to do the work of checking element visibility via the intersection observer API. Intersection observer is easier to use and read than code relying on various event handlers, because developers only need to register an observer to watch elements rather than writing tedious element visibility detection code.Abumaizer pro asked 2 years ago.

Dawid Adach pro commented 2 years ago. Abumaizer pro commented 2 years ago.

lazy load w3school

Abumaizer pro answered 2 years ago. You can find licensing details on our license page. Abumaizer pro asked 2 years ago 0 0. Dawid Adach pro commented 2 years ago Dear Abumaizer, could you please make your question more detailed? I am not sure which exactly config do you mean? Abumaizer pro commented 2 years ago I keep getting this error during lazy loading even after updating to the last version. It should only be imported in your application's main module. Error: ToastModule is already loaded.

Abumaizer pro commented 2 years ago yes the module is imported in other modules too. Now I changed the implementation, I imported ToastModule. Lazy loaded modules should use RouterModule.

Error: RouterModule. Add comment.

Lazy Loading Routes in Angular

Abumaizer pro answered 2 years ago 0 0 Best answer. Please insert min. Specification of the issue. About author. For any technical questions please use Support You can find licensing details on our license page. Your name. Your email.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. My organisation are an ecommerce company and have a numberv of pages displaying a long list of products, some pages can have 20 products while others may have up to ! I have been tasked with improving the load times of these pages, profiling shows that the majority of the load time is from the markup - there is too much of it!!

Due to the amount of info the business must show the markup cannot really be reduced. This leads me to looking at alternatives and one would be lazy loading of the product markup as the user scrolls down the screen we currently use this technique for product images.

Does anyone have any experience with doing such a thing that they could share? You can dynamically load content while scrolling. You can load all key data in your barebones HTML and then add necessary markup flourish with Javascript. One thing to look at is adding in compression to what the browser is sending. This will substantially reduce the page payload.

lazy load w3school

As others have mentioned, loading page content can cause a number of problems, especially for users with accessibility needs which is a much larger percentage than most people think. Always small pieces are created duration ms and insert into the dom. After around 50ms setTimeout the next piece is created and inserted into the dom. If the element is accessed the second time, it takes only 1ms Samsung S3. Hope this helps. Learn more. Asked 9 years ago. Active 5 years, 5 months ago.

Viewed 5k times. Is pagination an option? Active Oldest Votes. Dynamically loading content when scrolling cripples your browsers in-page search functionality. Many people use this, especially for long lists on pages like this. Yes, this is not friendly to page search. After around 50ms setTimeout the next piece is created and inserted into the dom b Android specific: I noticed that the first selection of an DOM element e.Images are critical for every website and application today.

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Whether it be marketing banners, product images or logos, it is impossible to imagine a website without images. Sadly though, images are large in size making them the single largest contributor to the page size. Now, since we cannot do away with images, we need to make our web pages load fast with them.

In this guide, we will talk about lazy loading images, a technique that helps improve the page load time and reduces page size, while still retaining all the images on the page. Click here to download the infographic. Before we move further, here is a sample video demonstrating the working of lazy loading. Notice how, when the page is scrolled, the grey placeholder is replaced with the actual image.

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Lazy Loading Images refer to a set of techniques in web and application development that defer the loading of images on a page to a later point in time - when those images are actually needed, instead of loading them up front.

Similarly, lazy loading defers the loading of resources on the page till they are actually needed. Instead of loading these resources as soon as the page loads, which is what normally happens, the loading of these resources is put off till the moment the user actually needs to view them. The technique of lazy loading can be applied to almost all the resources on a page.

For example, in a single page application, if a JS file is not needed until later, it is best not to load it initially. If an image is not needed up front, load it later when it actually needs to be viewed.

Lazy Loading defers the loading of an image that is not needed on the page immediately. An image, not visible to the user when the page loads, is loaded later when the user scrolls and the image actually becomes visible. If the user never scrolls, an image that is not visible to the user never gets loaded.

This is the most important one for you as a website administrator - better performance and load time. With lazy loading, you are reducing the number of images that need to be loaded on the page initially.

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Lesser resource requests mean lesser bytes to download and lesser competition for the limited network bandwidth available to the user.

This ensures that the device is able to download and process the remaining resources much faster. Hence, the page becomes usable much sooner as compared to one without lazy loading.

The second benefit for you is in terms of delivery costs. Image delivery, or delivery of any other asset, is usually charged on the basis of the number of bytes transferred.

Lazy Loading Images

As mentioned earlier, with lazy loading, if the image is not visible, it never gets loaded. Thus, you reduce the total bytes delivered on the page. This reduction in bytes transferred from your delivery network reduces delivery costs. This will become more apparent as we explore lazy loading further. The basic idea of lazy loading is simple - defer loading anything that is not needed right now. For images it usually translates to any image that is not visible to the user up front can be lazy loaded.

As the user scrolls down the page, the image placeholders start coming into viewport visible part of the webpage. We trigger the load for these images when they become visible.