A comprehensive guide to lazy loading in Angular.

Nov 15, 2023 |
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Angular is a popular JavaScript framework for developing dynamic web applications. Among its plethora of impressive capabilities, lazy loading is an ace up its sleeve that can significantly improve the efficiency and user experience of your Angular applications. Lazy loading enables you to load specific components of your application only when they are required, hence lowering initial load time and enhancing overall performance.

If you are looking for a beginner friendly comprehensive guide to lazy loading, then you are at the right place. In this in-depth article, we’ll look at what lazy loading is, why it’s important, and how to use it in your Angular applications. First, let us outline the entire journey we are about to embark on as below:

  • Understanding lazy loading
  • Why lazy loading is important
  • Lazy loading in angular
  • Implementing lazy loading in angular
  • Best practices for lazy loading

Understanding lazy loading

Simply put, lazy loading is a web development strategy that delays the loading of specific assets or components until they are needed. It means loading modules, components, or routes only when a user navigates to a specified portion of the application in the context of Angular. This strategy differs from eager loading, in which all of the application’s assets are loaded when the program is first loaded.

You may drastically reduce the initial load time of your Angular application by using lazy loading, which is especially important for large-scale applications with several components and routes. Users benefit from faster page loads and increased performance since they only download the code they require when they require it.

Why lazy loading is important

  • Faster initial load: Lazy loading makes your application load faster at first since it just loads the parts needed to render the initial view. Users can begin interacting with your app sooner.
  • Reduced payload size: By loading only the modules and components that are required, you can reduce the size of the initial bundle. Smaller bundles result in faster download times, which is especially important on slower internet connections.
  • Better user experience: Shorter load times result in a better user experience. Users are more inclined to stick around if your app reacts swiftly and smoothly.
  • Efficient resource utilization: Lazy loading allows you to efficiently manage resources. Unneeded code and assets are only loaded when they are required, decreasing server and client resource use.
  • Simplified code maintenance: Dividing your application into smaller, lazy-loaded modules makes managing and maintaining your codebase easier. You can work individually on different portions of your application.

Lazy loading in Angular

Angular’s routing architecture includes built-in support for lazy loading. When a user navigates to a specified route, the Angular router allows you to design routes that load modules or components on-demand. To accomplish this, Angular use the route configuration’s ‘loadChildren’ parameter.

Here’s an example of a lazy-loaded route in Angular:

const routes: Routes = [
{ path: ‘home’, component: HomeComponent },
{ path: ‘products’, loadChildren: () => import(‘./product/product.module’).then(m => m.ProductModule) },
// Other routes…

When a user navigates to the ‘products’ route in the snippet above, Angular will load the ‘ProductModule’ lazily using the ‘import’ expression. This module comprises components, services, and other resources related to the application’s ‘products’ functionality.

Implementing lazy loading in Angular

Implementing lazy loading in Angular involves a few steps:

  1. Develop modules: To begin, divide your application into modules. Modules are used to aggregate together similar components, services, and other resources. Make a module for each feature or piece of your application that you want to load asynchronously.
  2. Set up routes: Then, in your Angular application, configure the routes. Define the routes for each module and use the ‘loadChildren’ property to load the associated module in the background.
  3. Make use of the router outlet: Use the ‘router-outlet>/router-outlet>’ element in your application’s HTML template to designate where the lazy-loaded components should be rendered when a user navigates to a specific route.
  4. Build and deploy: When you build your Angular application, make sure your server is set to handle lazy-loaded routes appropriately. Ensure that the relevant module files are served when the client requests them.

That’s all! Your Angular application is now configured to use lazy loading, and components or modules will be loaded as users move across it.

Best practices for lazy loading

  • Plan your modules: Carefully plan and organize your modules based on the features of your application. Avoid making modules that are too large, as this defeats the idea of slow loading. Smaller modules are easier to handle and load more quickly.
  • Route preloading: You can use route preloading to load key modules in the background, ensuring they are ready when needed. Angular allows you to configure route preloading schemes.
  • Lazy loading approach: Determine the optimal lazy loading approach for your application. Consider whether you want to load modules per route or group comparable modules together for a better loading experience.
  • SEO optimization: Make sure search engines can crawl and index your lazy-loaded information. SEO optimization can be aided by Angular Universal, a server-side rendering solution.
  • Check performance: Use tools like Lighthouse or Web Vitals to continuously check the performance of your application. Identify and address any potential performance bottlenecks or concerns.
  • Code splitting: To further optimize the size of your bundles, use code splitting techniques provided by tools such as Webpack. As a result, your lazy-loaded modules may load faster.
  • User feedback: When a lazy-loaded module is loaded, provide feedback to users. To improve the user experience, this can take the form of a loading spinner or a progress indication.

Final thoughts

Lazy loading is a robust Angular method that can improve the efficiency and user experience of your web applications dramatically. You may cut initial load times, enhance resource efficiency, and simplify code maintenance by loading modules and components only when needed.

When implementing lazy loading in your Angular application, it’s critical to properly organize your modules, arrange routes effectively, and adhere to best practices to maximize speed. You may utilize lazy loading to create quick and responsive applications that keep consumers interested and satisfied.

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