VueJS

Content Distribution in Vue JS

Published Jul 23, 2020

Updated Jan 31, 2023

7 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This article was written over 18 months ago and may contain information that is out of date.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.

Vue implements a content distribution API inspired by the Web Components spec draft, using the <slot> element to serve as distribution outlets for content.

It promotes building composable and reusable components. Many folks have been writing about, or discussing, best practices, how to build components, how they communicate with each other, and how they should be structured in an app.

In this article, we'll dive head-first into Vue.js Slots, and Scoped Slots concepts, and go through code samples.

##Slots A Slot is a placeholder that allows content projection from a parent component to a child component.

The Vue engine, at runtime, processes the parent template, pulls the dynamic content, and injects it inside the Slot placeholder in the child component. In general, the child component hosts the <slot> element, and the parent component specifies the content to go inside it.

Figure 1 shows the interaction between a parent and child component.

| Parent and child component

Figure 1: Parent and child component

Basically, Slots are used for building Layout components (also known as Master Pages), base components (Button, Hyperlink and the like) or any other type of composable components to provide flexibility for component consumers to inject dynamic content at runtime.

Let’s create a Button component with a <slot> element.

<template>
  <button>
    <slot>Click Me</slot>
  </button>
</template>

The Button component is basic and contains a single <button> element. The button wraps a <slot> component with a default fallback text. This means, if the parent component didn’t provide any content for the Slot, it will be replaced at runtime with the default fallback text Click Me.

Let's embed this Button component inside a parent component.

<template>
    <Button></Button>
</template>

The child component Button is embedded into the parent component like any other normal component in Vue.js. Notice that in the code snippet above, the parent component is not injecting any content. When you run the app, you will see an HTML <button> element with the default fallback text. Figure 2 shows the app running.


Figure 2: Slot with default content

Let's inject some other text instead of the default fallback text, and run the app again. You have multiple choices when it comes to injecting content.

Without <template> element

<Button>
  Pretty Nice Button!
</Button>

With <template> element

<Button>
  <template v-slot:default>
    Pretty Nice Button!
  </template>
</Button>

Personally, I prefer the option using <template> element. The template content will be rendered in place of the <slot> element.

The <slot> element has a special attribute called name. This allows you to embed multiple Slots in your component, each designated with a different Slot name.

A <slot> element without a name attribute is considered the default Slot. To provide content for a <slot> element, you would use the v-slot directive, and then specify the name of the Slot.

In this code snippet, we could have removed the v-slot:default as this is the only <slot> element in the component. But, as a best practice, and in case you add more Slots in the future, I’d recommend you stick to this naming convention by using the v-slot:default.

You can play with this example on codesandbox.io.

Let's assume the Button component has another slot:

<template>
  <button>
    <slot>Click Me</slot>
    <br>
    <slot name="footer"/>
  </button>
</template>

Inside the parent component:

<template>
    <Button>
      <template v-slot:default>Pretty Nice Button!</template>
      <template v-slot:footer>Footer!</template>
    </Button>
</template>

There are two <template> elements, each for a specific slot.To add content to the default <slot> element, you add the v-slot:default directive by specifying the name of the slot. For the footer Slot, you provide the v-slot:footer directive to target the footer <slot> element.

Now, it makes more sense to use the v-slot directive on both Slots to differentiate them, and make your code readable.

You can play with this example on codesandbox.io.

##Slots and Props Thus far, we have seen how to use <slot> elements, and inject content to them. In some other cases, you might need to pass data to Slots.

Slots are generally compiled under the parent’s component context. This means whatever content you project inside a <slot> element is aware of the parent’s context only. For instance, if you have an interpolation or binding projected inside the <slot> element, these will be compiled with respect to the parent component, and not the child component. A code snippet is worth a thousand words.

<template>
    <Button>
      <template v-slot:default>
        {{ text }}
      </template>
    </Button>
</template>

<script>
import Button from "./components/Button";

export default {
  components: {
    Button
  },
  data() {
    return {
      text: 'Pretty Nice Button!',
    };
  },
};
</script>

The {{ text }} interpolation is referencing a local data variable defined on the component named text. The Vue.js engine compiles the projected content inside the parent component scope, and embeds the results into the child component.

You can play with this example on codesandbox.io.

A <slot> element can also render default fallback text passed from the parent component to the child component. How? Nothing special really. It's similar to how you pass data to Vue components via props.

Let's introduce a new text property on the Button component:

<template>
  <button>
    <slot>{{ text }}</slot>
  </button>
</template>

<script>
export default {
  props: {
    text: {
      type: String,
      default: "Click Me"
    }
  }
};
</script>

In the parent component:

<template>
  <div id="app">
    <h2>Vue Slots Demo</h2>
    <Button v-bind:text="text"></Button>
  </div>
</template>

<script>
import Button from "./components/Button";

export default {
  components: {
    Button
  },
  data() {
    return {
      text: "Pretty Nice Button!!!!"
    };
  }
};
</script>

You make use of Vue.js binding convention to bind the text prop on Button component to a local variable also named text. That’s all!

You can play with this example on codesandbox.io.

You can even go wild and accept a prop of type Function on the child component! The child component can share its context with the parent component. The parent component can then manipulate the child component context and return whatever content back to the child component.

The child component accepts a prop of type Function:

<template>
  <button>
    <slot>{{ textFnc('Hi from child!') }}</slot>
  </button>
</template>

<script>
export default {
  props: {
    textFnc: {
      type: Function
    }
  }
};
</script>

The default fallback content inside the child component calls the prop Function passing some random text.

The parent component defines the prop Function as follows:

<template>
  <div id="app">
    <h2>Vue Slots Demo</h2>
    <Button v-bind:textFnc="(prefix) => prefix + ' - ' + message"></Button>
  </div>
</template>

<script>
import Button from "./components/Button";

export default {
  components: {
    Button
  },
  data() {
    return {
      message: "Pretty Nice Button!!!!"
    };
  }
};
</script>

The function textFunc() executes under the parent component context. In this case, the function returns the text received from the child component, and appends it to a message that’s local to the parent component. The end result is shown in Figure 3.


Figure 3: Function prop

You can play with this example on codesandbox.io.

The takeaway, in using functions as props, is the ability to share the child component’s context with the parent component.

##Scoped Slots Passing functions as props to a child component is one way of sharing context between child and parent components. However, this method is limited to text only. The function defined on the parent component can only return text.

What if you want the parent component to pass HTML content to the child component’s slot(s) and also make use of the child component context? This is where Scoped Slots play their part.

Pretty complicated right? Well, not as complicated as you might think. Let’s check it out together!

Let's build a List component that owns an array of objects with a title and description properties.

<template>
  <ul>
    <li v-for="item in items" :key="item.id">
      <slot :item="item">
        <p>
          {{ item['title'] }}
          <br>
          {{ item['description'] }}
        </p>
      </slot>
    </li>
  </ul>
</template>

<script>
export default {
  props: {
    items: {
      type: Array,
      default: () => []
    }
  }
};
</script>

The component uses a <ul> element to loop over the items in the array. An <li> element is used to represent a single item. The code places a <slot> element inside each and every <li> element. The slot is bound to the single item object. In addition, the <slot> element defines a default fallback content.

Let’s switch to the parent component:

<template>
  <div id="app">
    <h2>Vue Slots Demo</h2>
    <List :items="items" />
  </div>
</template>

<script>
import List from "./components/List";

export default {
  components: {
    List
  },
  data() {
    return {
      items: [
        {
          id: 1,
          title: "Item #1",
          description: "Item #1 description"
        },
        {
          id: 2,
          title: "Item #2",
          description: "Item #2 description"
        },
        {
          id: 3,
          title: "Item #3",
          description: "Item #3 description"
        },
        {
          id: 4,
          title: "Item #4",
          description: "Item #4 description"
        },
        {
          id: 5,
          title: "Item #5",
          description: "Item #5 description"
        }
      ]
    };
  }
};
</script>

The component binds the items array property to the List component property items. It uses the default fallback content coming from the child component.

Figure 4 shows the app running:


Figure 4: List component with default fallback content

Let’s see how we can make use of the Slot binding.

As a refresher, the child component defines the following:

<slot :item="item">
  <p>
    {{ item['title'] }}
    <br>
    {{ item['description'] }}
  </p>
</slot>

The <slot> element binds the item object on the Slot. It also provides a default fallback content. What if the parent component wants to replace this default content with a new content? That's easy!

Let's change the parent component as follows:

<template>
  <List :items="items">
    <template v-slot:default="prop">
      <strong>{{ prop.item.title }}</strong>
    </template>
  </List>
</template>

The code snippet provides a <template> with a v-slot:default directive. The value given to the v-slot:default directive is actually the directive value representing the object passed in by the <slot> element defined inside the child component.

As a side note, I am writing another article, to be published very soon, exploring custom directives in Vue.js. Stay tuned!

Going back to the code snippet, the parent component now has access to the child component represented by the v-slot:default directive value.

The <template> element replaces the default fallback content by rendering just the title field and making it bold.

Figure 5 shows the app running:


Figure 5: List component with custom content

Scoped Slots is a powerful tool in Vue.js to allow you to build composable and reusable components.

##Slots in Vue 3 The content on Slots and Scoped Slots in this article applies to both Vue 2 and Vue 3. I am not aware of any change up until this moment. Things might change with the final release of Vue 3, but we’ll have to wait and see together!

##Conclusion Vue Slots feature gives developers the flexibility needed to build reusable and composable components in their applications.

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About the author(s)

Bilal Haidar
Author, Developer, and Mentor: Professional ASP.NET 3.5 Security, Membership, and Role Management with C# and VB | A Complete Guide to VueJS
@bhaidar @bhaidar

Making Seamless Page Transitions with the View Transitions API

Make Seamless Page Transitions using the View Transitions API Traditionally web applications have always had a less polished experience, both functionally and visually speaking, compared to native applications on mobile and other platforms. This has been improving over the years with the introduction of new web APIs and standards. One such new API that bridges that gap is the View Transitions API. What is the View Transitions API? The View Transitions API is a new browser feature that allows developers to more easily create animated transitions between pages and views, similar to how mobile apps have transitions when navigating between pages. Adding view transitions to your application can reduce the cognitive load on your users and make the experience feel less inconsistent. One great thing about view transitions is that they can be used by both SPAs (single-page applications) and MPAs (multi-page applications) alike! Using the View Transitions API for SPAs Let’s see how we can use view transitions ourselves. We will use examples adapted from demos created by the wonderful Jake Archibald and Bramus. There are some alterations to a few of the examples to make them work with the newest version of the View Transitions API, but otherwise, they’re mostly the same. The process of getting view transitions working for SPAs is as simple as calling document.startViewTransition right before starting navigation and replacing your page’s content immediately after that. You need to make this call in your router or in an event listener that triggers your page navigation. The following is an example of how you can hook into page navigation in a vanilla JavaScript application. This example uses the Navigation API if it’s available. As of the time of writing this article only Chromium-based browsers support the Navigation API, but there is a fallback to using a click listener on link elements so that this works with Firefox and Safari. ` If you’re using a framework, then there’s probably a better way to do this specific to that framework than by using this contrived example. For example, if you are implementing usage of this API with a Next application, you may opt for something like next-view-transitions. For this article, we’re going to focus on the way this is done in vanilla JavaScript so that the fundamentals of using the API are understood. Knowing how it’s implemented in vanilla JavaScript should give you enough understanding to implement this in the framework of your choice if there isn’t already a library that does it for you. Now we have a way to know when a navigation is being requested. Using the above utility function we can start the animation and replace our content as follows: ` getMyPageContentSomehow can be any function that returns HTML. How that is implemented will depend on your application and framework of choice. If you want to run these examples on your machine, the demo repository has instructions in its README. In essence, it’s as simple as hosting an HTTP server at the root of the project and visiting localhost. No fancy build system is required! By default, a fade is done that only lasts for a moment. The animation that happens can be configured using CSS with the ::view-transition-group pseudo-element on the element you want to animate, which in our case is the entire page, and we pass in root. ` Given that the animation properties are used, you have much control over what kind of animation to do. You can change the duration and the interpolation, add keyframes and gradients, and even add image masks. You can learn more about the animation properties in CSS on MDN. Using the View Transitions API for MPAs As mentioned, view transitions also work for MPAs with no client-side routing. Setting up view transitions for MPAs is much easier than for SPAs. All you have to do is include the CSS rule on all pages where you want the animations. ` Of course, like how it works with SPAs, you can customize the animations to your heart’s content using the view transition pseudo-elements. Conclusion I hope this article helped you understand the fundamentals of using the View Transitions API. Now that most browsers support it and it’s not too difficult to add it to existing applications, it is a great time to learn how to use it. You can view a full list of examples here (made by Jake Archibald and Bramus) if you want to see how advanced the animations can get. I like the Star Wars ones especially. The README explains how to get all the examples up and running (a total of 43!)....

Aug 2, 2024

4 mins

JavaScript

Introduction to Zod for Data Validation

As web developers, we're often working with data from external sources like APIs we don't control or user inputs submitted to our backends. We can't always rely on this data to take the form we expect, and we can encounter unexpected errors when it deviates from expectations. But with the Zod library, we can define what our data ought to look like and parse the incoming data against those defined schemas. This lets us work with that data confidently, or to quickly throw an error when it isn't correct. Why use Zod? TypeScript is great for letting us define the shape of our data in our code. It helps us write more correct code the first time around by warning us if we are doing something we shouldn't. But TypeScript can't do everything for us. For example, we can define a variable as a string or a number, but we can't say "a string that starts with user_id_ and is 20 characters long" or "an integer between 1 and 5". There are limits to how much TypeScript can narrow down our data for us. Also, TypeScript is a tool for us developers. When we compile our code, our types are not available to the vanilla JavaScript. JavaScript can't validate that the data we actually use in our code matches what we thought we'd get when we wrote our TypeScript types unless you're willing to manually write code to perform those checks. This is where we can reach for a tool like Zod. With Zod, we can write data schemas. These schemas, in the simplest scenarios, look very much like TypeScript types. But we can do more with Zod than we can with TypeScript alone. Zod schemas let us create additional rules for data parsing and validation. A 20-character string that starts with user_id_? It's z.string().startsWith('user_id_').length(20). An integer between 1 and 5 inclusive? It's z.number().int().gte(1).lte(5). Zod's primitives give us many extra functions to be more specific about *exactly* what data we expect. Unlike TypeScript, Zod schemas aren't removed on compilation to JavaScript—we still have access to them! If our app receives some data, we can verify that it matches the expected shape by passing it to your Zod schema's parse function. You'll either get back your data in exactly the shape you defined in your schema, or Zod will give you an error to tell you what was wrong. Zod schemas aren't a replacement for TypeScript; rather, they are an excellent complement. Once we've defined our Zod schema, it's simple to derive a TypeScript type from it and to use that type as we normally would. But when we really need to be sure our data conforms to the schema, we can always parse the data with our schema for that extra confidence. Defining Data Schemas Zod schemas are the variables that define our expectations for the shape of our data, validate those expectations, and transform the data if necessary to match our desired shape. It's easy to start with simple schemas, and to add complexity as required. Zod provides different functions that represent data structures and related validation options, which can be combined to create larger schemas. In many cases, you'll probably be building a schema for a data object with properties of some primitive type. For example, here's a schema that would validate a JavaScript object representing an order for a pizza: ` Zod provides a number of primitives for defining schemas that line up with JavaScript primitives: string, number, bigint, boolean, date, symbol, undefined, and null. It also includes primitives void, any, unknown, and never for additional typing information. In addition to basic primitives, Zod can define object, array, and other native data structure schemas, as well as schemas for data structures not natively part of JavaScript like tuple and enum. The documentation contains considerable detail on the available data structures and how to use them. Parsing and Validating Data with Schemas With Zod schemas, you're not only telling your program what data should look like; you're also creating the tools to easily verify that the incoming data matches the schema definitions. This is where Zod really shines, as it greatly simplifies the process of validating data like user inputs or third party API responses. Let's say you're writing a website form to register new users. At a minimum, you'll need to make sure the new user's email address is a valid email address. For a password, we'll ask for something at least 8 characters long and including one letter, one number, and one special character. (Yes, this is not really the best way to write strong passwords; but for the sake of showing off how Zod works, we're going with it.) We'll also ask the user to confirm their password by typing it twice. First, let's create a Zod schema to model these inputs: ` So far, this schema is pretty basic. It's only making sure that whatever the user types as an email is an email, and it's checking that the password is at least 8 characters long. But it is *not* checking if password and confirmPassword match, nor checking for the complexity requirements. Let's enhance our schema to fix that! ` By adding refine with a custom validation function, we have been able to verify that the passwords match. If they don't, parsing will give us an error to let us know that the data was invalid. We can also chain refine functions to add checks for our password complexity rules: ` Here we've chained multiple refine functions. You could alternatively use superRefine, which gives you even more fine grained control. Now that we've built out our schema and added refinements for extra validation, we can parse some user inputs. Let's see two test cases: one that's bound to fail, and one that will succeed. ` There are two main ways we can use our schema to validate our data: parse and safeParse. The main difference is that parse will throw an error if validation fails, while safeParse will return an object with a success property of either true or false, and either a data property with your parsed data or an error property with the details of a ZodError explaining why the parsing failed. In the case of our example data, userInput2 will parse just fine and return the data for you to use. But userInput1 will create a ZodError listing all of the ways it has failed validation. ` ` We can use these error messages to communicate to the user how they need to fix their form inputs if validation fails. Each error in the list describes the validation failure and gives us a human readable message to go with it. You'll notice that the validation errors for checking for a valid email and for checking password length have a lot of details, but we've got three items at the end of the error list that don't really tell us anything useful: just a custom error of Invalid input. The first is from our refine checking if the passwords match, and the second two are from our refine functions checking for password complexity (numbers and special characters). Let's modify our refine functions so that these errors are useful! We'll add our own error parameters to customize the message we get back and the path to the data that failed validation. ` Now, our error messages from failures in refine are informative! You can figure out which form fields aren't validating from the path, and then display the messages next to form fields to let the user know how to remedy the error. ` By giving our refine checks a custom path and message, we can make better use of the returned errors. In this case, we can highlight specific problem form fields for the user and give them the message about what is wrong. Integrating with TypeScript Integrating Zod with TypeScript is very easy. Using z.infer<typeof YourSchema> will allow you to avoid writing extra TypeScript types that merely reflect the intent of your Zod schemas. You can create a type from any Zod schema like so: ` Using a TypeScript type derived from a Zod schema does *not* give you any extra level of data validation at the type level beyond what TypeScript is capable of. If you create a type from z.string.min(3).max(20), the TypeScript type will still just be string. And when compiled to JavaScript, even that will be gone! That's why you still need to use parse/safeParse on incoming data to validate it before proceeding as if it really does match your requirements. A common pattern with inferring types from Zod schemas is to use the same name for both. Because the schema is a variable, there's no name conflict if the type uses the same name. However, I find that this can lead to confusing situations when trying to import one or the other—my personal preference is to name the Zod schema with Schema at the end to make it clear which is which. Conclusion Zod is an excellent tool for easily and confidently asserting that the data you're working with is exactly the sort of data you were expecting. It gives us the ability to assert at runtime that we've got what we wanted, and allows us to then craft strategies to handle what happens if that data is wrong. Combined with the ability to infer TypeScript types from Zod schemas, it lets us write and run more reliable code with greater confidence....

Nov 15, 2024

7 mins

JavaScriptZod

Making sense of Multiple v-model Bindings in Vue 3

This article is one of a series of articles on what’s new in Vue 3. If you haven’t checked that series yet, you can do so by visiting the links below: - Take your App to the Next Level with Vue 3 - Async Components in Vue 3 - Teleporting in Vue 3 - Your first Vue 3 app using TypeScript - Vue 3 Composition API, do you really need it? In this installment, I will introduce the new v-model in Vue 3 and go through a new feature that allows you to use multiple v-model on the same component! By design, the v-model directive allows us to bind an input value to the state of an app. We use it to create a two-way data binding on the form input, textarea, and select elements. It handles updates in two opposite directions: When the input value changes, it reflects the value onto the state inside the Component. When the Component state changes, it reflects the changes onto the form input elements. The core concept of v-model remains the same in Vue 3 with more enhancements and features. Let’s dig in! Vue 2: v-model Vue 2 supports a single v-model on any given Component. In Vue 2, to build a complex Component that supports two-way data binding, it utilizes a single v-model with one full-blown payload. The Component handles the state internally for all the input elements. It generates a single payload object representing the state of the Component. Finally, it emits an event to the parent Component with the payload attached. This method had several pitfalls, especially for creating Vue UI Libraries. Of these pitfalls is the vagueness of the payload interface. It’s unclear what’s being included in the payload. A developer had to loop through the payload object in order to uncover what properties were there. Another is the need to write the logic inside the Component to handle the internal state and the generation of the payload object. Shortly, we will uncover what has been improved in this regard with Vue 3. However, before this, let’s review some basics on how Vue 2 handles implementing two-way data binding in Components. Vue 2: Two-way Data Binding As mentioned, Vue 2 uses the v-model directive to support two-way data binding on Components. Internally, it follows certain steps and rules in order to support the v-model directive. By default, the v-model directive uses different properties and emits different events for different input elements: Text and Textarea elements use the value property and the input event Checkboxes and Radio buttons use the checked property and the change event Select fields use the input property and the change event. Building a Component with a single input element will internally use something similar to the snippet below: ` The custom Component above defines a single prop named value as follows: ` Then, in the parent Component, you use the new custom Component as follows: ` The v-model directive assumes that the CustomComponent defines an internal property named value and emits a single event named input. What if the CustomComponent has to handle multiple inputs? How do we accomplish that in Vue 2? Well, there is no official solution. However, there are two methods that you can use: The CustomComponent defines a single property named value of type Object. Internally, it parses the object into data fields and does the mapping manually on the template. On every change of any of the fields, it prepares a payload for all the fields and emits a single input event, and attaches the payload. That’s a lot of code to write for such a custom component. The other option is to skip using the v-model directive and instead utilize individual input/event pairs. I will illustrate this in a moment. Assuming you have a custom Component to handle the user’s first name and last name, you would employ something similar: ` As for the properties, the Component defines the following: ` Finally, the parent Component uses the new component as follows: ` We are not using the v-model anymore and providing multiple two-way data bindings on the new component. Further your understanding by reading the official docs on Using v-model on Components Vue 3: v-model In Vue 3, the v-model directive has had an overhaul to give developers more power and flexibility when building custom components that support two-way data binding. The v-model directive now supports new defaults. The default v-model property is renamed to modelValue instead of the old name of value. The default v-model event is renamed to update:modelValue instead of the old name of input. You might be thinking that's more typing when using the new v-model directive. The Vue team are one step ahead and have given you a shorthand to use instead. Let’s rebuild the custom component using it. ` The custom component defines a single prop named modelValue as follows: ` Then, in the parent component, use the new custom component as follows: ` The new v-model directive offers the new shorthand that is used like this: ` The v-model directive assumes that the CustomComponent defines an internal property named modelValue and emits a single event named update:ModelValue. In case you don’t want to use the default naming convention, feel free to use another name. Just remember to be consistent when naming properties. Here’s an example of using a custom name for the modelValue property. ` The custom component above defines a single prop named modelValue as follows: ` Then, in the parent component, you use the new custom component like so: ` Notice the use of the property fullName instead of the default property name. Vue 3: Multiple v-model directive bindings I hope the Vue 3 shorthand form of the v-model directive has given you a "hand up". With this, the v-model gives the flexibility to use multiple v-model directives on a single component instance. The modelValue can be renamed to whatever you want, allowing you to do this! This great new feature eliminates the previous two solutions I offered up on handling complex custom components for Vue 2. Let's jump in and go through an example demonstration! Demo - Multiple v-model directive bindings Let’s build a custom Address component that can be embedded in any form to collect a user’s address. > You can play with the example live on: vue3-multiple-v-model. > You can check the source code for the example on: vue3-multiple-v-model. Figure 1 below shows the final app in action. Let’s start by building the HTML template of the new component. Figure 1 shows that all the fields used are of type input elements. Except for the last one which is a checkbox element. Therefore, it’s suffice to focus on a single input field that will eventually be replicated for the rest of fields. ` The address-line input field binds the :value directive and the @input event as per the new v-model directive specifications in Vue 3. The component defines the following property: ` The other fields follow the same structure and naming convention. Let’s look at the checkbox field and see how it’s defined: ` In the case of a checkbox field element, we bind to the :checked directive instead of the :value directive. Also, we use the @change event instead of the @input event as in the case of input field elements. The event name follows the same standard way of emitting events in the new v-model directive. The component defines the following property: ` Let’s now embed the new custom Address component into the App component: ` For each and every property on the custom component, we bind using the v-model:{property-name} format. The modelValue was replaced with the specific property names we have in hand. When there was a single input binding, the shorthand format was so much easier. However, when there are multiple input elements, the modelValue is in a league of its own! Now, let’s define the properties inside the App component using the new Composition API setup() function: ` You create a new reactive property with an object payload. Finally, you return the reactive property to the component and use it to set bindings on the custom Address component as follows: ` That’s it! Conclusion Vue 3 has many new features and improvements. Today, we saw how we use multiple v-model directives on a single component instance. There is so much more to learn and uncover in Vue 3. The coming installments of this series will continue to look at different features to help you move from Vue 2 to Vue 3. Happy Vueing!...

Nov 6, 2020

6 mins

Vue

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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