React image lazy load

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react image lazy load

If you have been looking for an alternative to pagination, infinite scroll is a good consideration. The reader should possess a working knowledge of React functional components. Some familiarity with React hooks will be beneficial but not required, as we will be taking a look at a few.

We would also have learned a few more things about React Hooks. With that you can be able to implement infinite scroll and image lazy loading in your React application where necessary. Representing the same data in the form of visual aid is simpler.

Shajia Abidi explains how powerful of a tool Leaflet is, and how a lot of different kinds of maps can be created. This API allows us to implement cool features such as infinite scroll and image lazy loading. The intersection observer is created by calling its constructor and passing it a callback and an options object. The callback is invoked whenever one element, called the targetintersects either the device viewport or a specified element, called the root.

We can specify a custom root in the options argument or use the default value. The IntersectionObserverEntry object describes an intersection change for one observed target element. Note that the callback should not handle any time-consuming task as it runs on the main thread. Let us now look at how to make use of this API in a real React app. The final version of our app will be a page of pictures that scrolls infinitely and will have each image loaded lazily.

To get started, clone the starter project from this URL. It has minimal setup and a few styles defined. Feel free to create a new project if you like.

Lazy Image loading in React JS

Make sure you have yarn package manager installed if you want to follow with the repo. You can find the installation instructions for your specific operating system here. To get the next ten pictures, we change the value of page to 1, then 2, and so on.

Firstly, we define a reducer function, imgReducer. This reducer handles two actions. The next step is to wire up this reducer to a useReducer hook.

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Once that is done, we get back two things:. You can learn more about the useReducer hook in the React documentation.Chrome will soon provide native support for lazy loading images, a technique that mobile web developers have been using for years to save user bandwidth and speed up page load times by deferring the load of assets below the fold.

In this post, I'll use the open source React Storefront framework as an example to walk through how to progressively enable this feature in your React app and discuss issues you need to know for server side rendering. This helps save bandwidth and improve page load times:. React Storefrontour open source React framework for eCommerce PWAs, has an Image component that provides lazy loading via react-visibility-sensor.

The Image component also does a few other things, like switching to amp-img when rendering AMP, downscaling images for smaller screen sizes to save bandwidth, and providing fallback images for URLs that fail to load. Each image can be configured with an aspectRatio prop. This prevents the neighboring elements from shifting position when the image eventually loads, which would result in a poor user experience.

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This implementation provides lazy-loading capability in all browsers. However, this method has some drawbacks. Every image needs its own visibility sensor instance, and a react render cycle is triggered every time the user scrolls to an image.

To do this we need to detect if the browser supports this functionality. We can do that with the following function:. Since React Storefront framework supports server-side rendering by default, we need to make sure that our code is running in the browser before attempting to detect the feature.

react image lazy load

Next, update the initial value of the renderImage state, which determines whether or not the img element is rendered:. Finally, add the loading prop to the img element so that the browser knows to lazy load the image:. Lazy loading image support will definitely improve website performance when rendering in Chrome, but it still has limitations. Instead, images can only be inserted into the DOM when the react app mounts, which will noticeably slow down perceived page speed, especially on slow connections where the JavaScript bundles might take longer to download.

This would allow the server to decide if it should return img elements during server side rendering rather than placeholders when the browser natively supports lazy loading. Most CDNs control caching through the vary header, which identifies which headers to use when computing the cache key. Varying based on user-agent is a great way to kill your cache hit ratios by fragmenting your cache.

If you agree, I ask you to post your support for the lazy load client hint in this ticket. One option is to just not render the images server side and let them populate client side when the react app mounts. However, you may find heuristics that can help. A final option is to use user-agent detection to serve an appropriate version of the server-side rendered page.

This does, however, require normalizing your cache keys appropriately otherwise you could fragment your cache significantly. In a future post, we'll show how you can take the pain out of normalizing your cache and server-side rendering via the Moovweb XDN 's edge side logic ESL.

Stay tuned! Stay up to date! Polyfilling lazy loading with react-visibility-sensor React Storefrontour open source React framework for eCommerce PWAs, has an Image component that provides lazy loading via react-visibility-sensor. Insights Moovweb. Share this.

react image lazy load

Subscribe to Insights Moovweb Stay up to date!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.

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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.

Lazy Loading Images

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.

All that's left to do for the developer is to decide what to do when an element is visible. Now let's see how we can use intersection observer in JavaScript to lazy load images using this markup pattern:. If intersection observer is available, we create a new observer that runs a callback when img. Check out this CodePen example to see this code in action. The drawback of intersection observer, however, is that while it has good support amongst browsersit's not universal.

You'll need to polyfill browsers that don't support it, or as the above code suggests, detect if it's available and subsequently fall back to older, more compatible methods.

While you should use intersection observer for lazy loading, your application requirements may be such that browser compatibility is critical. You can polyfill intersection observer support and this would be easiestbut you could also fall back to code using scrollresizeand possibly orientationchange event handlers in concert with getBoundingClientRect to determine whether an element is in the viewport.

Assuming the same markup pattern from before, the following JavaScript provides the lazy loading functionality:. This code uses getBoundingClientRect in a scroll event handler to check if any of img.

A setTimeout call is used to delay processing, and an active variable contains the processing state which is used to throttle function calls. As images are lazy loaded, they're removed from the elements array. When the elements array reaches a length of 0the scroll event handler code is removed. See this code in action in this CodePen example.

While this code works in pretty much any browser, it has potential performance issues in that repetitive setTimeout calls can be wasteful, even if the code within them is throttled. In this example, a check is being run every milliseconds on document scroll or window resize regardless of whether there's an image in the viewport or not.

Plus, the tedious work of tracking how many elements are left to lazy load and unbinding the scroll event handler are left to the developer.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.

react image lazy load

If nothing happens, download the GitHub extension for Visual Studio and try again. Supports IntersectionObserver and includes a HOC to track window scroll position to improve performance. LazyLoadImage includes several effects ready to be used, they are useful to add visual candy to your application, but are completely optional in case you don't need them or want to implement you own effect.

In that case, it's better to wrap the deepest common parent of those components with a HOC to track those events trackWindowScroll. You must set the prop scrollPosition to the lazy load components.

Why is it useful, then? Imagine you are going to lazy-load an image you have already loaded in the same page. In that case, there is no need to lazy-load it because it's already stored in the cache of the user's browser. You can directly display it. That warning might appear if there are two components using trackWindowScroll at the same time. Also, make sure you are passing down scrollPosition to all components wrapped inside trackWindowScroll.

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. React Component to lazy load images and components using a HOC to track window scroll position. JavaScript CSS. JavaScript Branch: master.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. 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.

Implementing Infinite Scroll And Image Lazy Loading In React

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.

Your script have a problem with concurrency. While you are lazy loading the image, and if the place holder is still in the clip rectangle and you are scrolling, you will request again and again the image until the image is totally loaded. You have to move out the callback function to remove image from array the first time you requested it.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.

This project is now currently maintained by ameerthehackerplease reach out to him on any issues or help. You should be aware that your component will only be mounted when it's visible in viewport, before that a placeholder will be rendered. So you can safely send request in your component's componentDidMount without worrying about performance loss or add some pretty entering effects, see this demo for more detail.

Pass a query selector string or DOM node. LazyLoad will attach to the window object's scroll events if no container is passed. In the first round of render, LazyLoad will render a placeholder for your component if no placeholder is provided and measure if this component is visible. Set height properly will make LazyLoad calculate more precisely.

You can also use css to set the height of the placeholder instead of using height. Useful for images or simple components. Say if you want to preload a component even if it's px below the viewport user have to scroll px more to see this componentyou can set offset props to On the other hand, if you want to delay loading a component even if it's top edge has already appeared at viewport, set offset to negative number.

Library supports horizontal lazy load out of the box. So when you provide this prop with number like it will automatically set left edge offset to and top edge to. If you provide this prop with array like [, ]it will set left edge offset to and top offset to Respond to resize event, set it to true if you do need LazyLoad listen resize event.

If lazy loading components inside a overflow container, set this to true.React Lazy Load is easy to use React component which helps you defer loading content in predictable way. You can also use component inside scrolling container, such as div with scrollbar. It will be found automatically.

Check out an example. The offset option allows you to specify how far below, above, to the left, and to the right of the viewport you want to begin displaying your content.

If you specify 0your content will be displayed as soon as it is visible in the viewport, if you want to load px below or above the viewport, use The offsetVertical option allows you to specify how far above and below the viewport you want to begin displaying your content. The offsetHorizontal option allows you to specify how far to the left and right of the viewport you want to begin displaying your contet. The offsetTop option allows you to specify how far above the viewport you want to begin displaying your content.

The offsetBottom option allows you to specify how far below the viewport you want to begin displaying your content. The offsetLeft option allows you to specify how far to left of the viewport you want to begin displaying your content. The offsetRight option allows you to specify how far to the right of the viewport you want to begin displaying your content.

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The throttle is managed by an internal function that prevents performance issues from continuous firing of scroll events. Using a throttle will set a small timeout when the user scrolls and will keep throttling until the user stops. The default is milliseconds. By default the throttling function is actually a debounce function so that the checking function is only triggered after a user stops scrolling. To use traditional throttling where it will only check the loadable content every throttle milliseconds, set debounce to false.

The height option allows you to set the element's height even when it has no content. Git github. Need private packages and team management tools?

Installation React Lazy Load requires React 0.

A Responsive Lazy-loading images in React

Keywords react reactjs react-component load lazy. Install npm i react-lazy-load Downloads Weekly DownloadsVersion 3. License MIT.

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