Angular 17

Angular, the popular JavaScript framework, continues its journey of updation with the release of version 17, bringing some new improvements, and new features, as well as some breaking changes and deprecations.

What’s new in Angular 17?

Deferrable Views

One of the standout features introduced in Angular v17 is deferrable views, which allow you to lazy load components, directives, and pipes within a section of their templates. This helps in more efficient rendering of large templates by deferring the loading of certain elements until they are needed. With the new @defer syntax, you can specify which parts of the template should be loaded lazily, improving the initial loading time and overall performance of Angular applications.

Built-in Control Flow

Angular v17 introduces a new block syntax for optimized, built-in control flow, resolving the issues faced with *ngIf, *ngSwitch, and *ngFor directives. The new syntax includes conditional statements, switch statements, and for loops, provide up to 90% faster performance for certain benchmarks. This enhancement streamlines the development process and enhances the readability of Angular templates.

New @angular/ssr Package

With Angular v17, the server-side rendering (SSR) have been integrated more directly into the Angular CLI tooling. The new @angular/ssr package replaces @nguniversal/express-engine and provides equivalent functionality for adding SSR support to Angular applications. The Angular CLI now includes commands to add SSR capabilities to existing projects that simplifies the setup process and improving the development experience.

New Lifecycle Hooks

To improve the performance of Angular’s SSR and SSG (static site generation), Angular v17 introduces a set of new lifecycle hooks. These hooks, including afterRender and afterNextRender, helps you to interact with elements safely and efficiently during the application lifecycle. By registering callbacks to be invoked after rendering, you can perform tasks such as instantiating third-party libraries or measuring element size without relying on DOM emulation.

Vite and esbuild as Default Builders

In Angular v17, the Vite and esbuild-powered build experience becomes the default builder for all new applications. This enhancement brings significant performance improvements, with up to 87% faster build times for SSR and SSG applications. Additionally, the Angular team is working on schematics to help migrate existing applications to the new builder, further improving the development workflow.

Dependency Injection Debugging in DevTools

Angular v17 introduces debugging APIs that enable you to inspect the injector tree and dependencies of Angular components directly within the browser DevTools. This enhancement provides greater visibility into the runtime behavior of Angular applications, simplifying the debugging process and improving the overall developer experience.

Experimental View Transitions Support

The View Transitions API introduced in Angular v17 helps in smooth transitions when changing the DOM, particularly when navigating between routes. With the new withViewTransitions feature in the Angular router, you can leverage the browser’s native capabilities to create animated transitions between routes, enhancing the user experience of Angular applications.

Major Changes in Angular v17

While the update to Angular v17 brings significant improvements, you also need to know about certain breaking changes that might impact existing applications:

• Node.js Version Requirement: Angular v17 now requires Node.js version v18.13 or newer. You need to ensure that the development environment meets this minimum version requirement to work with Angular v17 effectively.
• TypeScript Version Requirement: Angular v17 no longer supports TypeScript versions older than 5.2. you must upgrade to TypeScript 5.2 or later to align with the requirements of Angular v17.
• Zone.js Version Requirement: Angular v17 requires zone.js version 0.14.0 or newer. It no longer supports older versions of zone.js. You need to update their zone.js dependency to meet this requirement.
• Strict NgSwitch Check: The NgSwitch directive in Angular v17 now defaults to the strict equality operator (===) instead of the loose equality operator (==). This change may require you to adjust NgSwitch expressions or individual condition values to adapt with the stricter equality check.
• Routes with LoadComponent Data Inheritance: Child routes with loadComponent no longer automatically inherit their data from their parent by default. In Angular v17, the default paramsInheritanceStrategy is emptyOnly. If you want to inherit parent data in child routes then you must update the strategy to always.
• Router Absolute Redirect Behavior Change: Absolute redirects no longer prevent further redirects in Angular v17. You need to adjust route configurations to prevent infinite redirects, as the router now continues to process redirects after encountering an absolute redirect.
• Removal of Deprecated Methods: Angular v17 removes deprecated methods such as setupTestingRouter and malformedUriErrorHandler from the RouterModule.forRoot options. You should use alternative methods, such as RouterModule.forRoot or UrlSerializer.parse, to handle routing and URL parsing errors effectively.
• Removal of Zone.js Bundles: Zone.js bundles, including zone-testing-bundle and zone-testing-node-bundle, are removed in Angular v17. This change affects imports from dist/, requiring to update import paths accordingly.
• OnPush Dynamically Instantiated Components: For dynamically instantiated components marked with OnPush change detection strategy, Angular v17 executes ngDoCheck during change detection if the component is dirty. You need to update tests or logic within ngDoCheck for dynamically instantiated components accordingly.
• Relocation of Router Public Methods: Router public methods have been relocated to provideRouter and RouterModule.forRoot. You should configure properties such as setupTestingRouter, paramsInheritanceStrategy, and others in provideRouter or RouterModule.forRoot as they are no longer part of the Router’s public API.

Deprecations in Angular v17

Angular v17 also marks certain features for deprecation, which indicates it will not be usable in future.

• NgProbeToken: The NgProbeToken, which was previously used for debugging purposes, is no longer used internally due to the transition from View Engine to Ivy. As a result, the token serves no practical utility and can be safely removed from applications and libraries.
• AnimationDriver.NOOP: The AnimationDriver.NOOP symbol is deprecated in Angular v17. Now you need to use the NoopAnimationDriver instead of AnimationDriver.NOOP to maintain compatibility with future versions of Angular. This change ensures consistency to Angular’s deprecation policy.

Upgrade from Angular v16 to Angular v17

Before updating to Angular v17 you need to check:

• You are using a supported version of node.js before you upgrade your application. Angular v17 supports node.js versions: v18.13.0 and newer.
• You are using a supported version of TypeScript before you upgrade your application. Angular v17 supports TypeScript version 5.2 or later.
• You are using a supported version of Zone.js before you upgrade your application. Angular v17 supports Zone.js version 0.14.x or later.

Follow these steps to update your application:

• In the project directory of your Angular application, open a terminal or command prompt.
• Run the following command to update your application to Angular v17:

  ng update @angular/core@17 @angular/cli@17

• Now you need to configure setupTestingRouter, canceledNavigationResolution, paramsInheritanceStrategy, titleStrategy, urlUpdateStrategy, urlHandlingStrategy, and malformedUriErrorHandler in provideRouter or RouterModule.forRoot as these properties are now not part of the Router’s public API.
• You need to adjust the equality check for NgSwitch because now it uses === instead of ==. Angular will log a warning message for the usages where you’d need to provide an adjustment.
• In Angular v17, now if you want the child routes of loadComponent routes to inherit data from their parent then you need to specify the paramsInheritanceStrategy to always, which in v17 is now set to emptyOnly.

After You Update:

Once you have updated your application to v17, review your application and its interactions to ensure everything is working correctly. Make sure to test all functionalities and components to confirm that there are no regressions or unexpected behavior.

Recent Articles on Angular:

• Angular 17 Structural Directives
• Purpose of ProvidedIn in Angular
• Handle User Events in Angular Components
• Implementing Lazy Loading in Angular
• Passing data from Child to Parent Component in Angular
• Difference between @Injectable and @Inject Decorators
• Content Projection in Angular
• Attribute Directives in Angular
• Built-in directives in Angular
• Use of *ngIf and *ngFor Directives in Angular
• Purpose of NgModule Decorator in Angular
• Component Communication in Angular
• Describe the MVC framework in Angular
• Built-in Structural Directives in Angular
• Purpose of the ngOnInit() method in Angular

Conclusion

As Angular continues to evolve, updating applications to the latest version ensures access to new features, enhanced performance, and improved security. However, it’s important to be aware of breaking changes and deprecations to avoid any potential issues during the update process.