Improving Angular Performance Using @defer Directive

In this blog, we'll explore how to boost the performance of your Angular applications using the @defer directive. The `@defer` directive in Angular enhances performance by loading template parts conditionally, improving load times and user experience. It delays rendering until conditions are met, optimizing resource use and responsiveness.

Introduction

Performance optimization is key to making applications run faster and smoother. Angular, a popular framework for building web apps, has a new feature called the @defer directive to help with this. It improves load times and user experience. In this blog post, we'll break down what the @defer directive is, how it works, and how you can use it to enhance your Angular apps.

What is @defer?

The @defer directive in Angular helps you load certain parts of a template only when needed, based on a condition you set. This can make your app more efficient by only rendering elements when they are necessary, For example, it can wait until a user clicks a button or a part of the screen becomes visible before loading and displaying that content. This way, your app only loads what's necessary, making it faster and more efficient.

Syntax

@defer () {
} @placeholder () {
} @loading () {
} @error {
}

@defer Directive

This is used to delay the loading of a template fragment until certain conditions are met.

1. on <trigger>: Specifies an event that triggers the deferred loading. Here is one simple example of on viewport trigger

   @defer (on viewport) {
     <component />
   }
   

   (on viewport) specifies that the deferred rendering should happen when the element comes into the viewport.
2. when <condition>: Defines the condition that needs to be true before the template is loaded.
3. prefetch on <trigger>: Optionally, you can prefetch the content based on a trigger.
4. prefetch when <condition>: Optionally, you can prefetch the content when a certain condition is true.

@placeholder Directive

This defines what should be shown while the deferred content is being loaded.

@loading Directive

This defines the content to be shown while the deferred content is actually loading.

@error Directive

This defines what should be shown if there's an error during the loading process.

In short, this syntax lets you control when different parts of your Angular template appear and what to show while you’re waiting, depending on different conditions and triggers.

Benefits of Using @defer directive

1. Faster Loading: By delaying less important content, your app loads quicker and feels smoother to use.
2. Better User Experience: Users see the key parts of your app right away, while the less important stuff loads in the background, so the app stays responsive.
3. Efficient Use of Resources: By waiting to display parts of your app that aren’t needed right away, you free up your browser’s resources, making everything run more smoothly.

Summary

The @defer directive in Angular helps make your app run better and faster. It allows you to delay loading some parts of your app until they're really needed. This way, your app stays quick and responsive, even if it has a lot of data or complex tasks. Using @defer can make your app perform better and provide a smoother experience for users.

Please let me know in the comments area if you have any questions.