Let’s assume we have a very small web shop with 4 files: Without digging too much into details let’s see how those files are distributed across the application: In above code, depending on the current route we are dynamically importing either product or category modules and then running init function that is exported by both of them. Display a loading state while data is being fetched. Thankfully Vue has a very useful feature called async components that solves this problem gracefully. By default, v-model syncs the input with the data after each input event (with the exception of IME composition, as stated above). In the first part of this series you read that generally speaking we can assume that any lazily loaded resource is downloaded when it’s import() function is invoked and in case of Vue component that happens only when component is requested to render. For example if we’re in a Category page of ecommerce shop we could prefetch Product page because there is a high chance user will visit it. Code splitting is just a process of splitting the app into this lazily loaded chunks. Next is the setI18nLanguage function that will actually change the language in our vueI18n instance, axios and where ever else is needed. The reason why I’m still writing this article is, that I wanted a more lightweight solution. This is why the trick with v-if works. Important: Depending on your build configuration prefetching might work only on production mode. Ok, we know what lazy loading is and that it’s pretty useful. Now when you click the button, you will lazy load the GreetComponent inside the parent component. You can read more about this behavior here. We can then download this optional chunk later, when needed. The navigator object holds information about the browser. Objective. For those still not convinced if it is worth playing with lazy loading, here’s some raw numbers from the simple example we’ve been using. // src/utils/lazy-load-component.js export default function lazyLoadComponent ({ componentFactory , loading , loadingData , }) { let resolveComponent ; return () => ({ // We return a promise to resolve a // component eventually. It turns out that the solution is extremely simple. I have a problem that, in the architecture of my apps, I want to load all the components of my application asynchronally. Especially lack of the Safari support can be painful. Bing is a good example - 2 seconds of delay resulted in a 4.3% loss in revenue per visitor for them. Or there might be modals, tooltips and other parts and components that are not needed on every page. Then we are creating a loadedLanguages array that will keep track of our loaded languages. The data changes pretty infrequently, and is only required in certain workflows. …that’s all you need! This series is based on learnings from Vue Storefront performance optimization process. Chúng ta sẽ gọi file này là ImageItem.vue. While mobile-first approach becomes a standard and uncertain network conditions are something we should always take into consideration it’s harder and harder to keep your application loading fast. When building apps with a bundler, the JavaScript bundle can become quite large, and thus affect the page load time. During my daily job I build open source products, interfaces for programmers and engage communities. This is where we’ll define our API: basi­cal­ly, what data are we return­ing.Our API is incred­i­bly sim­ple, we just want to be able to load the next 9 blog entries. So it turns out that all we need to do to lazily load any component is combining v-if directive and dynamic import statement like this: Lazy loading components can save a lot of time on initial download, but it comes with a price that the user has to pay later. It’s important to note that the prefetching will only start after the browser has finished the initial load and becomes idle. But what if we need our Cat module only under certain circumstances like a response to a user interaction? Everything marked as red is something that is not needed on current route and can be lazily loaded. A Vue.js plugin for lazyload your Image or Component in your application. It’s time to see how we can make use of it in our Vue applications. The answer to this question is trivial and intuitive - everything that is not required on initial render. Vue’s async component feature and webpack’s code splitting feature made it easy to lazy-load route components.. To know more about that implementation, you may check my earlier artilce on that here Now the component will be downloaded only when it’s requested. Async components are also wrapped in a function, like dynamic imports are. Those components are usually good candidates to be loaded lazily. Async component is basically an object containing: The second property is a great way to deal with browsers that don’t support prefetching while the third one let us deal with error handling in offline-first application in rare cases when the prefetching fails. You can add the lazy modifier to instead sync after change events: < input v-model.lazy = "msg" >.number Technically, both are valid choices - it ultimately depends on the user experience you are aiming for. We need a way to tell our application when it should download this chunk of code. Now take a look at this example: Let’s take a quick look at what happened here: Instead of directly importing Cat module we created a function that returns the import() function. Lazy loading Vue components. This asynchronous behavior is called lazy loading and allows for a smaller initial bundle size. Part 1 — Introduction to performance optimization and lazy loading. Prefetching seems to solve all of our problems but browser support for this feature is not there yet for some of them. We can easily load some parts of our application lazily with webpack dynamic imports. Such delay is much worse for components than whole pages because we’re not used to wait for individual parts of the UI to appear. This is where dynamic imports can help us! So they can be consumed in the same way any component is. So after we’ve down­loaded & installed the Ele­ment API plu­g­in, we’ll need to cre­ate a file called elementapi.php and put it in our craft/config fold­er. In most cases, you don’t need all the code from your Javascript bundle immediately when a user visits your website. Lazily loaded routes is a popular technique for faster page loading by splitting the build file into many chunks and load it on demand. On the other hand, lazy loading refers to an approach where all of the scripts are not loaded on the DOM as the application starts, instead, they are only loaded when requested, making the JavaScript bundle size very small at … It's a big problem affecting the user experience because the visitors have to wait before accessing the content. Most of the tips in this series will focus on making our JS bundle smaller. Tạo một component ImageItem. Web developer passionate about newest web technologies with special love for Vue and Progressive Web Apps. Part 1 — Introduction to performance optimization and lazy loading. In other words we are just creating some kind of a new entry point for the dependency graph. The bigger bundle, the longer it takes to download and parse for our users. Even though this technique will give you a massive size reduction there are still plenty of things that we can lazy load … Vue.js - The Progressive JavaScript Framework. There are various npm packages for infinite scroll that you can use for your Vue app, but some of these may be overkill. We learned how to use lazy loading with Vue components. By lazy loading proper components and libraries we managed to cut off the bundle size of Vue Storefront by 60%! When building apps with a bundler, the JavaScript bundle can become quite large, and thus affect the page load time. The good news is that it’s extremely easy and we can lazily load the entire Single File Component, with it’s CSS and HTML with the same syntax as … To prefetch any resource (usually we prefetch the code-splitted ones like off-screen components or routes) the only thing that you need to do is put it into a tag. It’s called prefetching. Lazy Loading Images in VueJS is important to save bandwidth, rank your page better, improve performance considerably and provide a better User Experience, especially if your website has several images . While bundling our assets Webpack is creating something called Digital Fortress. The goal of this post is to show one way to do this division and how to load each file asynchronously, only when the component is requested from a route change. Thanks to the relatively new Intersection Oberserver API and the concept of Async Components in Vue.js, we can implement a lazy loading utility function rather easily. This is how I made use of async components in Vue Storefront default theme: TIP: You can display different error message if fetching fails due to a lack of network connectivity by using navigator.onLine property. Now we should be able to see how much of the downloaded code was actually used. dependency graph (click here to see how it looks like). According to RAIL model guidelines every user input should generate a response in under 100ms.It is almost impossible to achieve such a low response time if we have to download resources before the application is able to respond. To start with your Vuetify background image app, you can use the VueJS CLI.Go to your development folder, open a terminal and start typing: Let’s dig a little bit deeper. When we click a button, we expect a reaction immediately. A simple lazy-load list component based Vue 2.x, which will be on-demand rendering the list based container element's viewport. In this series I’ll dig deep into Vue performance optimization techniques that we are using in Vue Storefront and that you can use in your Vue.js applications to make them loading instantly and perform smooth. Everything that was imported inside this part will be bundled together so productGallery will end up in the same bundle as product module. Output bundle is just a single (or multiple as we will see in the later parts) javascript file containing all modules from the dependency graph. It’s time to see how we can use lazy loading in our own Vue.js applications. About; Contact; Write for Us! Support images lazyload in window or build-in element. Grouping Components in the Same Chunk; Extending RouterLink; Navigation Failures; Dynamic Routing; Migrating from Vue 2 # Lazy Loading Routes. Versatile. To see how much of the JavaScript code is actually used in our website we can go to the devtools -> cmd+shift+p -> type coverage -> hit ‘record’. So what we can do? pages/index.vue shows how to lazy load a component by prefixing it with the word "Lazy". In this article, I'll show you how Vue 3 helps you to do this with new APIs. Our users will need to download them at some point, which means they have to wait for the postponed resource to be downloaded. Webpack is using this dependency graph to detect which files it should include in the output bundle. TIP: If you’re using Vue CLI 3 every lazily loaded resource is prefetched by default! As we can see even vuejs.org has a huge room for improvement ;). Now webpack will bundle the content of the dynamically imported module into a separate file. To understand while it’s crucial first we need to understand how Webpack is bundling all of our files. We’ll call this file ImageItem.vue. Simply put this comment inside dynamic import function like in the example below and your resource will be prefetched: At the moment of code execution webpack will look for every magic comment like this and dynamically (which means at the code execution time, not in a build time) add tag to section of your application: Now when user will request chunk with ModalWindow.vue it will already be in a memory and appear instantly. It’s time to see how we can make use of it in our Vue applications. Vue-Lazyload. Lazy loading allows us to split the bundle and serve only the needed parts so users are not wasting time to download and parse code that’ll not be used. During my daily job I build open source products, interfaces for programmers and engage communities. How cool is this? This usually means everything that the user doesn’t see until he/she interacts with our app in some way. In the tests that I’ve done, Vue-Lazyload adds about 19 kB to the final bundle size (overall bundle size: 106 kB). Bài viết này tôi sẽ cùng bạn tạo một ví dụ lazy loading Image bằng VueJS. Now that we know what lazy loading is and why we need it. Link Making an API. Continuing my dive into the Intersection Observer API, this week I look at probably the most practical use case for them, lazy loading images! That’s probably the easiest way to gain some performance boost. Even though this technique will give you a massive size reduction there are still plenty of things that we can lazy load to save even more of it. In this tutorial, we will show you some techniques of lazy load images using JavaScript. The function representing dynamically imported module returns a Promise that will give us access to the exported members of the module while resolved. The bundle is essentially our entire application’s JavaScript. v2-lazy-list. $ vue init webpack-simple infinite-scroll-vuejs Getting Initial User Data. It’s not so easy when we use webpack that generates names of our bundles depending on order of module resolution (for example entry point becomes main.js, first code-splitted element encountered by webpack becomes 0.js, next one 1.js etc). Passing Data to Lazy-Loaded Component. Interesting side note: If you’re using Nuxt.js every in currently opened route will prefetch it’s content automatically. Lazy loading is one of the best ways to make your web app more performant and reduce the bundle size. If we import a JavaScript module in a standard way like this: It will be added as a node of a main.js in the dependency graph and bundled with it. Learn how to lazy load routes with a free lesson on Vue School. The longer a user has to wait, the more likely he is to leave our site. Hãy bắt đầu bằng việc tạo một component hiển thị một hình ảnh (đương nhiên là chưa có lazy load gì cả). Here are the most common ways to invoke dynamic loading of Vue component: Please note that the invocation of lazyComponent function will happen only when component is requested to render in a template. The good news is that it’s extremely easy and we can lazily load the entire Single File Component, with it’s CSS and HTML with the same syntax as previously! Web developer passionate about newest web technologies with special love for Vue and Progressive Web Apps. Vue module for lazy-loading images in your vue.js applications. As a summary, bigger bundle = fewer users, which can be directly translated to a loss of potential revenue. Let’s see another example that will better illustrate this mechanism. A small size Vue.js directive for lazy loading images using IntersectionObserver API - mazipan/vue-tiny-lazyload-img An implication of that behavior is that with v-show component is always downloaded, no matter what’s the value inside it and for v-if directive component is downloaded only after it’s value will become true so remember that you should always use v-if with lazy loaded components! Lazy-loading components is a great way to improve the user experience of your app. Learn more in the Directory Structure book in the Components chapter. Co-founder of Vue Storefront, author of StorefrontUI and Vue.js community partner. Data Fetching; Scroll Behavior; Lazy Loading Routes. That’s all! - hilongjw/vue-lazyload In the previous article, we’ve seen that we can drastically reduce bundle size by lazy loading every route in separation. Vue Vue.js VueJS. Now that you can call yourself master of lazy loaded components! It is important to understand exactly when a code-splitted component is fetched. In the next part we will learn when it’s wise to lazy load third party libraries, how to identify which one of them are too big and how to easily find smaller equivalents. It’s time to master another area of Vue performance! In this series, I’ll dig deep into Vue performance optimization techniques that we are using in Vue Storefront and that you can use in your Vue.js applications to make them loading instantly and perform smooth. The answer is easy — lazy loading and code splitting. Knowing how dynamic imports are working we know that product and category will end up in a separate bundles but what will happen with productGallery module that wasn’t dynamically imported? In this article we digged really deep into lazy loading of individual components. Assuming we have a file called main.js specified as an entry point in our webpack config it will be a root of our dependency graph. Data Fetching; Composition API; Transitions; Scroll Behavior; Lazy Loading Routes. .lazy. It would be more efficient if we can split each … If nothing happens when we interact with a website, we either perceive the application as slow or broken, and most of us leave the site. The purpose of lazy loading is to postpone downloading parts of your application that are not needed by the user on the initial page load which ends up in much better loading time. Eager loading is the default approach of loading JavaScript code on to the DOM, for Vue JS this means using the import statement to bring in a component into the app.vue file. My goal is to make this series a full and complete guide on Vue apps performance. An incrementally adoptable ecosystem that scales between a library and a full-featured framework. For example this code: The component will not be loaded until it is required in the DOM, which is as soon as the v-if value changes to true. Now every js module that we will import in this file will become its node in the graph and every module imported in these nodes will become their nodes. Project Creation We can illustrate this process with below image: Now that we know how bundling works, it becomes obvious that the bigger our project gets, the bigger the initial JavaScript bundle becomes. In short we are creating a new VueI18n instance as we normally would. Lazy Background Images for Vue 2, is a component which can help you load images directly using a URL or loading them dynamically. My goal is to make this series a full and complete guide on Vue apps performance. nuxt.config.js shows components: true for auto importing components. Webpack’s magic comments are special phrases that are affecting build process when used in a comment. What problem does this feature solve? By using below techniques we were able to cut off size of our initial bundle by 70% and made it load in a blink of an eye. By making a dynamic import we are basically isolating the given node (in that case Cat) that will be added to the dependency graph and downloading this part when we decide it’s needed (which implies that we are also cutting off modules that are imported inside Cat.js). Laravel + Vue = Love . In the next part of this series I’ll show you the most useful (and also the fastest) way to gain some significant performance boost on any Vue.js application. One of such magic comments is /* webpackPrefetch: true */. In the previous article, we’ve seen that we can drastically reduce bundle size by lazy loading every route in separation. Angular allows us to pass data to @Input() decorated properties and handle events of lazy-loaded components using the instance property of the lazy-loaded component. I'm trying to determine the best approach for implementing lazy loading of this data - I only want to ask the server for it the first time I need it, cache it in the store, and use the cached value for as long as its valid. Fortunately there is a feature that can help us easily prefetch any resource - magic comments. We will walk you through some techniques to lazy loading images that can improve user experience and increase the number of your web visitors. That can result in bad or extremely bad user experience, depending on how long time it takes to download the resource. Prefetching allows us to eliminate bad UX consequence of lazy loading without affecting page performance at all. Single-file (.vue) components