What’s New in Angular 19?

TL;DR: Angular 19 makes standalone components the default, streamlining development and enabling a strict mode for enforcement. It also introduces incremental hydration for performance and better state management using linkedSignal.

Angular 19 brings its latest update, continuing its tradition of delivering stable and robust enhancements to modern web applications. This release focuses on improving flexibility, scalability, and performance while simplifying the developer experience.

Key highlights include:

• Incremental hydration: This feature supports high-performance use cases, with control over rendering on the client, server, or during builds, and prerendered route parameters.

• Reactivity improvements: Stabilization of core reactivity primitives and the introduction of linkedSignal and resource for better state management.

• Developer-friendly schematics: Updated tools for best practices, including inputs, outputs, queries, dependency injection, and the new build system.

• Standalone defaults and strict enforcement: Angular 19 streamlines standalone components with a schematic to update metadata and a compiler flag to enforce modern APIs by identifying non-standalone abstractions.

Angular 19 continues to set the standard for building efficient, scalable apps with an optimized developer experience.

Incremental hydration

Angular 19 lets you control when specific parts of your template load and become interactive. Using familiar syntax like @defer, you can instruct Angular to download and hydrate components only when certain triggers occur, such as a user interaction or a component entering the viewport.

Imagine a blog page where the main article loads instantly, but the comments section and related posts load only when the user scrolls down to interact with them. This ensures the page loads faster, focusing on the most important content first.

With incremental hydration, Angular allows you to defer loading parts of your app using @defer, making it both efficient and seamless. Here’s how it works:

• The main article is fully loaded and interactive when the page opens.

• The comments section only loads when the user scrolls down to it.

• The related posts load on-demand when the user clicks on a button to view them.

Refer to the following code example to enable incremental hydration.

import { provideClientHydration, withIncrementalHydration } from '@angular/platform-browser';
// Enable incremental hydration
provideClientHydration(withIncrementalHydration());

Refer to the template code below.

<!-- Main article loads immediately -->
<h1>Understanding Incremental Hydration</h1>
<p>This article explains how incremental hydration improves performance...</p>

<!-- Comments section loads when it enters the viewport -->
@defer (hydrate on viewport) {
  <comments-section></comments-section>
}

Experimental linked signals

Angular’s linkedSignal simplifies managing state that depends on other states, ensuring automatic updates and easier dependency tracking. This is useful when UI elements’ states depend on others and need to reset under certain conditions.

Consider a user profile where the theme setting is linked to the region. When a user selects a theme, it updates the profile, but when the region changes (e.g., switching from US to EU), the theme should reset to the default for that region.

With linkedSignal, you can create a dynamic relationship between the region and theme, ensuring that the theme resets automatically when the region changes.

Refer to the following code example.

// Define user region and available themes for each region
const region = signal('US'); // Default region
const themes = signal({
  US: 'light',
  EU: 'dark',
  APAC: 'blue'
});

// Create a linked theme signal that defaults to the region's theme
const theme = linkedSignal(() => themes()[region()]);
console.log(theme()); // light (US default)

// Change the theme preference manually
theme.set('dark');
console.log(theme()); // dark

// When the region changes, the theme resets to the region's default theme
region.set('EU');
console.log(theme()); // dark (EU default)

In this code, we define two signals: region, which stores the user’s current region (defaulted to US), and themes, which holds the available themes for each region. Then, a theme signal is created using linkedSignal to automatically link the theme to the current region’s default theme. Initially, the theme is set to light (the default for US). When the user manually changes the theme using theme.set(‘dark’), it updates to dark. However, when the region is changed to EU, the theme signal automatically resets to dark, as it’s the default for the EU region.

Introducing resource() in Angular v19: Simplifying asynchronous data handling

Angular v19 introduces the resource API, a new way to manage asynchronous data with the power of signals. This API helps you handle data fetching—such as API calls—while maintaining reactivity and simplicity within your Angular components.

A resource consists of:

1. Request function: Defines what data needs to be fetched, like a product ID.

2. Loader: Handles the asynchronous operation, such as making an HTTP request.

3. Resource instance: Provides signals for the state of the request, including loading, success, or error states.

Let’s say you need to fetch product details based on a product ID. Using resource(), you can manage the entire process seamlessly:

export class ProductDetailComponent {
    productId = input<number>();

    productService = inject(ProductService);

    product = resource({
      request: (id) => `api/products/${id}`,
      loader: async ({ request }) => await this.productService.getProduct(request),
    });
  }

In this example, the product automatically tracks the loading state and fetches data, reducing the need for manual management of loading or error states.

The resource() API simplifies handling asynchronous data in Angular by automatically managing the loading, value, and error states. It’s an easy way to integrate async operations with Angular’s reactive system, ensuring cleaner, more efficient code.

Standalone defaults and strict enforcement

In Angular v19, standalone components are now the default. This means that when you generate new components, they will automatically be created as standalone, removing the need for the standalone: true declaration. This change streamlines development and simplifies component management.

To ensure your project adheres to modern Angular standards, the strictStandalone compiler flag has been introduced. When enabled, it will throw an error if any component, directive, or pipe is not standalone. To activate this feature, simply add the following configuration to your angular.json:

{
    "angularCompilerOptions": {
        "strictStandalone": true
    }
}

Other features to consider

Angular v19 introduces several key updates: the Effects API enhances support for asynchronous operations, while Zoneless Angular improves performance by eliminating the need for zones in change detection. Angular Material and the CDK are further advanced for better accessibility and design. A new feature now warns about unused imports in standalone components, and the –define flag simplifies environment variable declaration in the command line. Additionally, local variables in templates are now supported, improving code readability.

Conclusion

Thanks for reading! Angular v19 brings several exciting new features designed to enhance performance, simplify development, and improve the overall developer experience. Key highlights include incremental hydration, which enables more efficient loading of components based on user interaction, and linkedSignal, which simplifies state management by linking dependent signals. The new resource() API improves the handling of asynchronous data by automatically managing loading and error states.

Angular v19 also makes standalone components the default, streamlining component creation and introducing a strictStandalone flag to enforce modern API standards. With improvements to the Effects API, Zoneless Angular, Angular Material, and the CLI, this update further solidifies Angular’s commitment to providing efficient, scalable solutions for modern web apps.

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