Angular

NgRx Facade Pattern

Published Feb 9, 2021

Updated Feb 14, 2023

4 min read

This article was written over 18 months ago and may contain information that is out of date. Some content may be relevant but please refer to the relevant official documentation or available resources for the latest information.

NgRx Facade Pattern

The NgRx Facade Pattern was first introduced by Thomas Burleson in 2018 and has drawn a lot of attention in recent years. In this article, we will discuss the pattern, how to implement it in Angular and discuss whether or not we should implement it.

What is NgRx?

First, what is NgRx?

NgRx is a state management solution for Angular built on top of RxJS which adheres to the redux pattern.

It contains an immutable centralized store where the state of our application gets stored.

We select slices of state from the Store using Selectors, which we can then render in our components.
We dispatch Actions to our Store.
Our Store redirects our Action to our Reducers to recalculate our state and replaces the state within our Store.

See the diagram below for an illustrated example:

This provides us with a tried and tested pattern for managing the state of our application.

What is the Facade Pattern?

Now that we know what NgRx is, what is the Facade Pattern?

Well, what are Facades?

Facades are a pattern that provides a simple public interface to mask more complex usage.

As we use NgRx more and more in our application, we add more actions and more selectors that our components must use and track. This increases the coupling between our component and the actions and selectors themselves.

The Facade pattern wants to simplify this approach by wrapping the NgRx interactions in one place, allowing the Component to only ever interact with the Facade. This means you are free to refactor the NgRx artefacts without worrying about breaking your Components.

In Angular, NgRx Facades are simply services. They inject the NgRx Store allowing you to contain your interactions with the Store in the service.

How do we implement it?

To begin with, let's show a Component that uses NgRx directly:

export class TodoListComponent implements OnInit {
  todoList$: Observable<Todo[]>;

  constructor(private store: Store<TodoListState>) {}

  ngOnInit() {
    this.todoList$ = this.store.select(getLoadedTodoList);

    this.loadTodoList();
  }

  loadTodoList() {
    this.store.dispatch(new LoadTodoList());
  }

  addNewTodo(todo: string) {
    this.store.dispatch(new AddTodo(todo));
  }

  editTodo(id: string, todo: string) {
    this.store.dispatch(new EditTodo({ id, todo }));
  }

  deleteTodo(id: string) {
    this.store.dispatch(new DeleteTodo(id));
  }
}

As we can see, this depends a lot on interactions with the Store and has made our component fairly complex and coupled to NgRx.

Let's create a Facade that will encapsulate this interaction with NgRx:

@Injectable({
  providedIn: 'root',
})
export class TodoListFacade {
  todoList$ = this.store.select(getLoadedTodoList);

  constructor(private store: Store<TodoListState>) {}

  loadTodoList() {
    this.store.dispatch(new LoadTodoList());
  }

  addNewTodo(todo: string) {
    this.store.dispatch(new AddTodo(todo));
  }

  editTodo(id: string, todo: string) {
    this.store.dispatch(new EditTodo({ id, todo }));
  }

  deleteTodo(id: string) {
    this.store.dispatch(new DeleteTodo(id));
  }
}

It's essentially everything we had in the component, except now in a service.

We then inject this service into our Component:

export class TodoListComponent implements OnInit {
  todoList$: Observable<Todo[]>;

  constructor(private todoListFacade: TodoListFacade) {}

  ngOnInit() {
    this.todoList$ = this.todoListFacade.todoList$;

    this.todoListFacade.loadTodoList();
  }

  addNewTodo(todo: string) {
    this.todoListFacade.addNewTodo(todo);
  }

  editTodo(id: string, todo: string) {
    this.todoListFacade.editTodo({ id, todo }));
  }

  deleteTodo(id: string) {
    this.todoListFacade.deleteTodo(id);
  }
}

By implementing the Facade and using it in our Component, our component no longer depends on NgRx and we do not have to import all actions and selectors.

The Facade hides those implementation details, keeping our Component cleaner and easier tested.

Pros

What are some advantages of using Facades?

It adds a single abstraction of a section of the Store.
- This service can be used by any component that needs to interact with this section of the store. For example, if another component needs to access the TodoListState from our example above, they do not have to reimplement the action dispatch or state selector code. It's all readily available in the Facade.
Facades are scalable
- As Facades are just services, we can compose them within other Facades allowing us to maintain the encapsulation and hide complex logic that interacts directly with NgRx, leaving us with an API that our developers can consume.

Cons

Facades lead to reusing Actions.
- Mike Ryan gave a talk at ng-conf 2018 on Good Action Hygiene which promotes creating as many actions as possible that dictate how your user is using your app and allowing NgRx to update the state of the application from your user's interactions.
- Facades force actions to be reused. This becomes a problem as we no longer update state based on the user's interactions. Instead, we create a coupling between our actions and various component areas within our application.
- Therefore, by changing one action and one accompanying reducer, we could be impacting a significant portion of our application.
We lose indirection
- Indirection is when a portion of our app is responsible for certain logic, and the other pieces of our app (the view layer etc.) communicate with it via messages.
- In NgRx, this means that our Effects or Reducers do not know what told them to work; they just know they have to.
- With Facades, we hide this indirection as only the service knows about how the state is being updated.
Knowledge Cost
- It becomes more difficult for junior developers to understand how to interact, update and work with NgRx if their only interactions with the state management solution are through Facades.
- It also becomes more difficult for them to write new Actions, Reducers and Selectors as they may not have been exposed to them before.

Conclusion

Hopefully, this gives you an introduction to NgRx Facades and the pros and cons of using them. This should help you evaluate whether to use them or not.

This Dot is a consultancy dedicated to guiding companies through their modernization and digital transformation journeys. Specializing in replatforming, modernizing, and launching new initiatives, we stand out by taking true ownership of your engineering projects.

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About the author(s)

Colum Ferry
JavaScript Developer and Enthusiast. Really enjoy working with Angular. Married with 2 amazing kids. Powered by Coffee.
@FerryColum @https://github.com/coly010

Exploring Angular Forms: A New Alternative with Signals

Exploring Angular Forms: A New Alternative with Signals In the world of Angular, forms are essential for user interaction, whether you're crafting a simple login page or a more complex user profile interface. Angular traditionally offers two primary approaches: template-driven forms and reactive forms. In my previous series on Angular Reactive Forms, I explored how to harness reactive forms' power to manage complex logic, create dynamic forms, and build custom form controls. A new tool for managing reactivity - signals - has been introduced in version 16 of Angular and has been the focus of Angular maintainers ever since, becoming stable with version 17. Signals allow you to handle state changes declaratively, offering an exciting alternative that combines the simplicity of template-driven forms with the robust reactivity of reactive forms. This article will examine how signals can add reactivity to both simple and complex forms in Angular. Recap: Angular Forms Approaches Before diving into the topic of enhancing template-driven forms with signals, let’s quickly recap Angular's traditional forms approaches: 1. Template-Driven Forms: Defined directly in the HTML template using directives like ngModel, these forms are easy to set up and are ideal for simple forms. However, they may not provide the fine-grained control required for more complex scenarios. Here's a minimal example of a template-driven form: ` ` 2. Reactive Forms: Managed programmatically in the component class using Angular's FormGroup, FormControl, and FormArray classes; reactive forms offer granular control over form state and validation. This approach is well-suited for complex forms, as my previous articles on Angular Reactive Forms discussed. And here's a minimal example of a reactive form: ` ` Introducing Signals as a New Way to Handle Form Reactivity With the release of Angular 16, signals have emerged as a new way to manage reactivity. Signals provide a declarative approach to state management, making your code more predictable and easier to understand. When applied to forms, signals can enhance the simplicity of template-driven forms while offering the reactivity and control typically associated with reactive forms. Let’s explore how signals can be used in both simple and complex form scenarios. Example 1: A Simple Template-Driven Form with Signals Consider a basic login form. Typically, this would be implemented using template-driven forms like this: ` ` This approach works well for simple forms, but by introducing signals, we can keep the simplicity while adding reactive capabilities: ` ` In this example, the form fields are defined as signals, allowing for reactive updates whenever the form state changes. The formValue signal provides a computed value that reflects the current state of the form. This approach offers a more declarative way to manage form state and reactivity, combining the simplicity of template-driven forms with the power of signals. You may be tempted to define the form directly as an object inside a signal. While such an approach may seem more concise, typing into the individual fields does not dispatch reactivity updates, which is usually a deal breaker. Here’s an example StackBlitz with a component suffering from such an issue: Therefore, if you'd like to react to changes in the form fields, it's better to define each field as a separate signal. By defining each form field as a separate signal, you ensure that changes to individual fields trigger reactivity updates correctly. Example 2: A Complex Form with Signals You may see little benefit in using signals for simple forms like the login form above, but they truly shine when handling more complex forms. Let's explore a more intricate scenario - a user profile form that includes fields like firstName, lastName, email, phoneNumbers, and address. The phoneNumbers field is dynamic, allowing users to add or remove phone numbers as needed. Here's how this form might be defined using signals: ` > Notice that the phoneNumbers field is defined as a signal of an array of signals. This structure allows us to track changes to individual phone numbers and update the form state reactively. The addPhoneNumber and removePhoneNumber methods update the phoneNumbers signal array, triggering reactivity updates in the form. ` > In the template, we use the phoneNumbers signal array to dynamically render the phone number input fields. The addPhoneNumber and removePhoneNumber methods allow users to reactively add or remove phone numbers, updating the form state. Notice the usage of the track function, which is necessary to ensure that the ngFor directive tracks changes to the phoneNumbers array correctly. Here's a StackBlitz demo of the complex form example for you to play around with: Validating Forms with Signals Validation is critical to any form, ensuring that user input meets the required criteria before submission. With signals, validation can be handled in a reactive and declarative manner. In the complex form example above, we've implemented a computed signal called formValid, which checks whether all fields meet specific validation criteria. The validation logic can easily be customized to accommodate different rules, such as checking for valid email formats or ensuring that all required fields are filled out. Using signals for validation allows you to create more maintainable and testable code, as the validation rules are clearly defined and react automatically to changes in form fields. It can even be abstracted into a separate utility to make it reusable across different forms. In the complex form example, the formValid signal ensures that all required fields are filled and validates the email and phone numbers format. This approach to validation is a bit simple and needs to be better connected to the actual form fields. While it will work for many use cases, in some cases, you might want to wait until explicit "signal forms" support is added to Angular. Tim Deschryver started implementing some abstractions around signal forms, including validation and wrote an article about it. Let's see if something like this will be added to Angular in the future. Why Use Signals in Angular Forms? The adoption of signals in Angular provides a powerful new way to manage form state and reactivity. Signals offer a flexible, declarative approach that can simplify complex form handling by combining the strengths of template-driven forms and reactive forms. Here are some key benefits of using signals in Angular forms: 1. Declarative State Management: Signals allow you to define form fields and computed values declaratively, making your code more predictable and easier to understand. 2. Reactivity: Signals provide reactive updates to form fields, ensuring that changes to the form state trigger reactivity updates automatically. 3. Granular Control: Signals allow you to define form fields at a granular level, enabling fine-grained control over form state and validation. 4. Dynamic Forms: Signals can be used to create dynamic forms with fields that can be added or removed dynamically, providing a flexible way to handle complex form scenarios. 5. Simplicity: Signals can offer a simpler, more concise way to manage form states than traditional reactive forms, making building and maintaining complex forms easier. Conclusion In my previous articles, we explored the powerful features of Angular reactive forms, from dynamic form construction to custom form controls. With the introduction of signals, Angular developers have a new tool that merges the simplicity of template-driven forms with the reactivity of reactive forms. While many use cases warrant Reactive Forms, signals provide a fresh, powerful alternative for managing form state in Angular applications requiring a more straightforward, declarative approach. As Angular continues to evolve, experimenting with these new features will help you build more maintainable, performant applications. Happy coding!...

Oct 4, 2024

5 mins

AngularJavaScript

How to build an AI assistant with OpenAI, Vercel AI SDK, and Ollama with Next.js

In today’s blog post, we’ll build an AI Assistant using three different AI models: Whisper and TTS from OpenAI and Llama 3.1 from Meta. While exploring AI, I wanted to try different things and create an AI assistant that works by voice. This curiosity led me to combine OpenAI’s Whisper and TTS models with Meta’s Llama 3.1 to build a voice-activated assistant. Here’s how these models will work together: * First, we’ll send our audio to the Whisper model, which will convert it from speech to text. * Next, we’ll pass that text to the Llama 3.1 model. Llama will understand the text and generate a response. * Finally, we’ll take Llama’s response and send it to the TTS model, turning the text back into speech. We’ll then stream that audio back to the client. Let’s dive in and start building this excellent AI Assistant! Getting started We will use different tools to build our assistant. To build our client side, we will use Next.js. However, you could choose whichever framework you prefer. To use our OpenAI models, we will use their TypeScript / JavaScript SDK. To use this API, we require the following environmental variable: OPENAI_API_KEY— To get this key, we need to log in to the OpenAI dashboard and find the API keys section. Here, we can generate a new key. Awesome. Now, to use our Llama 3.1 model, we will use Ollama and the Vercel AI SDK, utilizing a provider called ollama-ai-provider. Ollama will allow us to download our preferred model (we could even use a different one, like Phi) and run it locally. The Vercel SDK will facilitate its use in our Next.js project. To use Ollama, we just need to download it and choose our preferred model. For this blog post, we are going to select Llama 3.1. After installing Ollama, we can verify if it is working by opening our terminal and writing the following command: Notice that I wrote “llama3.1” because that’s my chosen model, but you should use the one you downloaded. Kicking things off It's time to kick things off by setting up our Next.js app. Let's start with this command: ` After running the command, you’ll see a few prompts to set the app's details. Let's go step by step: * Name your app. * Enable app router. The other steps are optional and entirely up to you. In my case, I also chose to use TypeScript and Tailwind CSS. Now that’s done, let’s go into our project and install the dependencies that we need to run our models: ` Building our client logic Now, our goal is to record our voice, send it to the backend, and then receive a voice response from it. To record our audio, we need to use client-side functions, which means we need to use client components. In our case, we don’t want to transform our whole page to use client capabilities and have the whole tree in the client bundle; instead, we would prefer to use Server components and import our client components to progressively enhance our application. So, let’s create a separate component that will handle the client-side logic. Inside our app folder, let's create a components folder, and here, we will be creating our component: ` Let’s go ahead and initialize our component. I went ahead and added a button with some styles in it: ` And then import it into our Page Server component: ` Now, if we run our app, we should see the following: Awesome! Now, our button doesn’t do anything, but our goal is to record our audio and send it to someplace; for that, let us create a hook that will contain our logic: ` We will use two APIs to record our voice: navigator and MediaRecorder. The navigator API will give us information about the user’s media devices like the user media audio, and the MediaRecorder will help us record the audio from it. This is how they’re going to play out together: ` Let’s explain this code step by step. First, we create two new states. The first one is for keeping track of when we are recording, and the second one stores the instance of our MediaRecorder. ` Then, we’ll create our first method, startRecording. Here, we are going to have the logic to start recording our audio. We first check if the user has media devices available thanks to the navigator API that gives us information about the browser environment of our user: If we don’t have media devices to record our audio, we just return. If they do, then let us create a stream using their audio media device. ` Finally, we go ahead and create an instance of a MediaRecorder to record this audio: ` Then we need a method to stop our recording, which will be our stopRecording. Here, we will just stop our recording in case a media recorder exists. ` We are recording our audio, but we are not storing it anywhere. Let’s add a new useEffect and ref to accomplish this. We would need a new ref, and this is where our chunks of audio data will be stored. ` In our useEffect we are going to do two main things: store those chunks in our ref, and when it stops, we are going to create a new Blob of type audio/mp3: ` It is time to wire this hook with our AudioRecorder component: ` Let’s go to the other side of the coin, the backend! Setting up our Server side We want to use our models on the server to keep things safe and run faster. Let’s create a new route and add a handler for it using route handlers from Next.js. In our App folder, let’s make an “Api” folder with the following route in it: We want to use our models on the server to keep things safe and run faster. Let’s create a new route and add a handler for it using route handlers from Next.js. In our App folder, let’s make an “Api” folder with the following route in it: ` Our route is called ‘chat’. In the route.ts file, we’ll set up our handler. Let’s start by setting up our OpenAI SDK. ` In this route, we’ll send the audio from the front end as a base64 string. Then, we’ll receive it and turn it into a Buffer object. ` It’s time to use our first model. We want to turn this audio into text and use OpenAI’s Whisper Speech-To-Text model. Whisper needs an audio file to create the text. Since we have a Buffer instead of a file, we’ll use their ‘toFile’ method to convert our audio Buffer into an audio file like this: ` Notice that we specified “mp3”. This is one of the many extensions that the Whisper model can use. You can see the full list of supported extensions here: https://platform.openai.com/docs/api-reference/audio/createTranscription#audio-createtranscription-file Now that our file is ready, let’s pass it to Whisper! Using our OpenAI instance, this is how we will invoke our model: ` That’s it! Now, we can move on to the next step: using Llama 3.1 to interpret this text and give us an answer. We’ll use two methods for this. First, we’ll use ‘ollama’ from the ‘ollama-ai-provider’ package, which lets us use this model with our locally running Ollama. Then, we’ll use ‘generateText’ from the Vercel AI SDK to generate the text. Side note: To make our Ollama run locally, we need to write the following command in the terminal: ` ` Finally, we have our last model: TTS from OpenAI. We want to reply to our user with audio, so this model will be really helpful. It will turn our text into speech: ` The TTS model will turn our response into an audio file. We want to stream this audio back to the user like this: ` And that’s all the whole backend code! Now, back to the frontend to finish wiring everything up. Putting It All Together In our useRecordVoice.tsx hook, let's create a new method that will call our API endpoint. This method will also take the response back and play to the user the audio that we are streaming from the backend. ` Great! Now that we’re getting our streamed response, we need to handle it and play the audio back to the user. We’ll use the AudioContext API for this. This API allows us to store the audio, decode it and play it to the user once it’s ready: ` And that's it! Now the user should hear the audio response on their device. To wrap things up, let's make our app a bit nicer by adding a little loading indicator: ` Conclusion In this blog post, we saw how combining multiple AI models can help us achieve our goals. We learned to run AI models like Llama 3.1 locally and use them in our Next.js app. We also discovered how to send audio to these models and stream back a response, playing the audio back to the user. This is just one of many ways you can use AI—the possibilities are endless. AI models are amazing tools that let us create things that were once hard to achieve with such quality. Thanks for reading; now, it’s your turn to build something amazing with AI! You can find the complete demo on GitHub: AI Assistant with Whisper TTS and Ollama using Next.js...

Sep 27, 2024

8 mins

AINextJSJavaScript

Best Practices for Managing RxJS Subscriptions

When we use RxJS, it's standard practice to subscribe to Observables. By doing so, we create a Subscription. This object provides us with some methods that will aid in managing these subscriptions. This is very important, and is something that should not be overlooked! Why do we care about subscription management? If we do not put some thought into how we manage and clean up the subscriptions we create, we can cause an array of problems in our applications. This is due to how the Observer Pattern is implemented. When an Observable emits a new value, its Observers execute code that was set up during the subscription. For example: ` If we do not manage this subscription, every time obs$ emits a new value doSomethingWithDataReceived will be called. Let's say this code is set up on the Home View of our App. It should only ever be run when the user is on the Home View. Without managing this subscription correctly when the user navigates to a new view in the App, doSomethingWithDataReceived could still be called, potentially causing unexpected results, errors or even hard-to-track bugs. So what do we mean by Subscription Management? Essentially, subscription management revolves around knowing when to complete or unsubscribe from an Observable, to prevent incorrect code from being executed, especially when we would not expect it to be executed. We can refer to this management of subscriptions as cleaning up active subscriptions. How can we clean up subscriptions? So, now that we know that managing subscriptions are an essential part of working with RxJS, what methods are available for us to manage them? Unsubscribing Manually One method we can use, is to unsubscribe manually from active subscriptions when we no longer require them. RxJS provides us with a convenient method to do this. It lives on the Subscription object and is simply called .unsubscribe(). If we take the example we had above; we can see how easy it is to unsubscribe when we need to: ` 1. We create a variable to store the subscription. 2. We store the subscription in a variable when we enter the view. 3. We unsubscribe from the subscription when we leave the view preventing doSomethingWithDataReceived() from being executed when we don't need it. This is great; however, when working with RxJS, you will likely have more than one subscription. Calling unsubscribe for each of them could get tedious. A solution I have seen many codebases employ is to store an array of active subscriptions, loop through this array, unsubscribing from each when required. Let's modify the example above to see how we could do this: ` 1. We create an array to store the subscriptions. 2. We add each subscription to the array when we enter the view. 3. We loop through and unsubscribe from the subscriptions in the array. These are both valid methods of managing subscriptions and can and should be employed when necessary. There are other options however, that can add a bit more resilience to your management of subscriptions. Using Operators RxJS provides us with some operators that will clean up the subscription automatically when a condition is met, meaning we do not need to worry about setting up a variable to track our subscriptions. Let's take a look at some of these! first The first operator will take only the first value emitted, or the first value that meets the specified criteria. Then it will complete, meaning we do not have to worry about manually unsubscribing. Let's see how we would use this with our example above: ` When obs$ emits a value, first() will pass the value to doSomethingWithDataReceived and then unsubscribe! take The take operator allows us to specify how many values we want to receive from the Observable before we unsubscribe. This means that when we receive the specified number of values, take will automatically unsubscribe! ` Once obs$ has emitted five values, take will unsubscribe automatically! takeUntil The takeUntil operator provides us with an option to continue to receive values from an Observable until a different, notifier Observable emits a new value. Let's see it in action: ` 1. We create a notifier$ Observable using a Subject. _(You can learn more about Creating Observables here.)_ 2. We use takeUntil to state that we want to receive values until notifier$ emits a value 3. We tell notifier$ to emit a value and complete _(we need to clean notifer$ up ourselves) when we leave the view, allowing our original subscription to be unsubscribed. takeWhile Another option is the takeWhile operator. It allows us to continue receiving values whilst a specified condition remains true. Once it becomes false, it will unsubscribe automatically. ` In the example above we can see that whilst the property finished on the data emitted is false we will continue to receive values. When it turns to true, takeWhile will unsubscribe! BONUS: With Angular RxJS and Angular go hand-in-hand, even if the Angular team has tried to make the framework as agnostic as possible. From this, we usually find ourselves having to manage subscriptions in some manner. async Pipe Angular itself provides one option for us to manage subscriptions, the async pipe. This pipe will subscribe to an Observable in the template, and when the template is destroyed, it will unsubscribe from the Observable automatically. It's very simple to use: ` By using the as data, we set the value emitted from the Observable to a template variable called data, allowing us to use it elsewhere in the children nodes to the div node. When the template is destroyed, Angular will handle the cleanup! untilDestroyed Another option comes from a third-party library developed by Netanel Basal. It's called until-destroyed, and it provides us with multiple options for cleaning up subscriptions in Angular when Angular destroys a Component. We can use it similarly to takeUntil: ` It can _also_ find which properties in your component are Subscription objects and automatically unsubscribe from them: ` This little library can be beneficial for managing subscriptions for Angular! When should we employ one of these methods? The simple answer to this question would be: > When we no longer want to execute code when the Observable emits a new value But that doesn't give an example use-case. - We have covered one example use case in this article: when you navigate away from a view in your SPA. - In Angular, you'd want to use it when you destroy Components. - Combined with State Management, you could use it only to select a slice of state once that you do not expect to change over the lifecycle of the application. - Generally, you'd want to do it when a condition is met. This condition could be anything from the first click a user makes to when a certain length of time has passed. Next time you're working with RxJS and subscriptions, think about when you no longer want to receive values from an Observable, and ensure you have code that will allow this to happen!...

Dec 14, 2020

5 mins

RxJSJavaScriptAngular

Understanding the Difference Between `:focus` and `:focus-visible` in CSS

Understanding the Difference Between :focus and :focus-visible in CSS I have learned my fair share about the importance of keyboard accessibility, so I know that visual indication of the focused element is very important. But the well-known :focus pseudo-class is not always the best fit for this job. That's where :focus-visible comes in. Let's look at the differences between these two pseudo-classes and explore the best practices for using them effectively. What is the :focus Pseudo-Class? The :focus pseudo-class is a CSS selector that applies styles to any element that receives focus, regardless of how that focus was triggered. This includes focus events from keyboard navigation, mouse clicks, and touch interactions. Example Usage of :focus ` In this example, the button will display a blue outline whenever it is focused, whether the user clicks on it with a mouse, taps it on a touchscreen, or navigates to it using the keyboard. What is the :focus-visible Pseudo-Class? The :focus-visible pseudo-class is more specialized. It only applies styles to an element when the browser determines that the focus should be visible. This typically occurs when the user navigates via the keyboard or assistive technologies rather than through mouse or touch input. Example Usage of :focus-visible ` Here, the button will only show a blue outline when focused through keyboard navigation or another input method that usually requires visible focus indicators. Key Differences Between :focus and :focus-visible :focus - Behavior: Applies to any element that receives focus, regardless of the input method. - Use Cases: Ensures that all interactions with the element are visually indicated, whether by mouse, keyboard, or touch. :focus-visible - Behavior: Applies styles only when the focus should be visible, such as using a keyboard or assistive technology. - Use Cases: Ideal for scenarios where you want to provide focus indicators only to keyboard and assistive technology users while avoiding unnecessary outlines for mouse and touch users, typically required by design. Accessibility Implications :focus - Pros: - Guarantees that all users can see when an element is focused, which is critical for accessibility. - Cons: - Can lead to a suboptimal experience for mouse users, as focus styles may appear unnecessarily during mouse interactions. :focus-visible - Pros: - Enhances user experience by showing focus indicators only when necessary, thus keeping the interface clean for mouse and touch users. - Tailors the experience for keyboard and assistive technology users, providing them with clear visual cues. - Cons: - Additional considerations may be required to ensure that focus indicators are not accidentally omitted, especially in older browsers that do not support :focus-visible. - There may be cases where you want to show focus indicators for all users, regardless of input method. Best Practices for Using :focus and :focus-visible To achieve the best accessibility and user experience, combining both :focus and :focus-visible in your CSS is often a good idea. Combining :focus and :focus-visible ` Here is a Stackblitz example of what such styling could look like for you to try out and play with. Additional Tips - Test with Keyboard and Assistive Technology: Ensure that your web application is navigable using a keyboard (Tab, Shift + Tab, etc.) and that focus indicators are visible for those who rely on them. It's never a bad idea to include accessibility testing in your e2e testing suite. - Provide Clear Focus Indicators: Make sure that focus indicators are prominent and easy to see. A subtle or hard-to-spot focus indicator can severely impact accessibility for users who rely on keyboard navigation. Conclusion The :focus-visible pseudo-class offers a more refined way to manage focus indicators, improving accessibility and user experience, particularly for keyboard and assistive technology users. By understanding the differences between :focus and :focus-visible, and applying best practices in your CSS, you can create more accessible and user-friendly web applications. Remember, accessibility should never be an afterthought. By thoughtfully applying focus styles, you ensure that all users, regardless of how they interact with your site, can easily navigate and interact....

Nov 8, 2024

3 mins

AccessibilityCSSPlaywright

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NgRx Facade Pattern

NgRx Facade Pattern

What is NgRx?

What is the Facade Pattern?

How do we implement it?

Pros

Cons

Conclusion

Colum Ferry

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