Angular 17 — Deferred Loading Using Defer Block

Angular 17 — Deferred Loading Using Defer Block

Angular 17 is a renowned JavaScript framework employed for crafting robust web applications, and it boasts an array of features to aid developers in constructing efficient and scalable applications. Among these features, one stands out - deferred loading, also known as lazy loading.

Deferred loading is a strategic approach that empowers you to load modules, components, and assets only when they are needed, rather than loading everything simultaneously when your application initializes. This technique can significantly enhance the performance and loading times of your application, particularly when dealing with extensive and intricate applications.

Angular 17 furnishes developers with various methods to implement deferred loading, and one of these methods is the "defer block." The defer block allows you to define a template that will only be loaded when specific conditions are met.

How to Utilize the Defer Block

To employ the defer block effectively, you must first define it within your component's template. This can be achieved using the {#defer} and {/defer} tags.

Inside the defer block, you have the liberty to specify the template you intend to load. This template can encompass HTML, CSS, and JavaScript to cater to your application's requirements.

Furthermore, you can delineate conditions that trigger the loading of the defer block. These conditions may be based on events, such as a user's interaction like clicking a button, or they could rely on the properties of the component.


Here's a practical example demonstrating the use of the defer block to perform lazy loading of a component:

<div class="my-component">
  <h1>My Component</h1>

  {#defer trigger="click"}

In this example, the "my-lazy-component" component will only be loaded when a user clicks on the "My Component" heading.

Additional Features of the Defer Block

Beyond specifying loading conditions, the defer block offers several other useful features:

  • Placeholder Content: You can define placeholder content that will be displayed while the defer block is loading, giving users visual feedback.

  • Loading Content: You have the ability to specify loading content that will be presented to users while the defer block fetches its dependencies.

  • Error Content: In case the defer block encounters an issue while loading, you can define error content to display an informative message to users.

Benefits of Leveraging the Defer Block

The defer block comes with a host of advantages, making it an invaluable tool in your Angular development arsenal:

  • Enhanced Performance: By loading modules, components, and assets only when they are needed, the defer block can significantly enhance your application's performance.

  • Reduced Bundle Size: It can help reduce the size of your application's bundle by only loading the assets required at the current point in time, leading to more efficient resource management.

  • Improved User Experience: Users are spared from waiting for unnecessary assets to load, leading to a smoother and more enjoyable user experience.

In Conclusion

The defer block stands as a formidable tool for implementing deferred loading in Angular 17 applications. Its ease of use and the manifold benefits it offers, such as enhanced performance, reduced bundle size, and an improved user experience, make it a compelling choice for developers, especially when working on large or complex Angular 17 applications. Therefore, if you're embarking on such a project, it is highly recommended to harness the power of the defer block to optimize your application's performance and user satisfaction.

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