Jeferson Brito

Posted on Sep 20, 2020 • Edited on Apr 4, 2021

Vue 3.0 is finally out!

#vue #javascript #webdev #tutorial

The new major version of Vue is here! after 2 years of development one of the most popular JavaScript frameworks is full of new capabilities and much more approachable for large applications.

We will go through some of the exciting new features and see how the new release will affect the way you write Vue Apps.

Breaking changes
How to Create a new Vue 3 App
New Global API
New Features
Further Reading

Breaking changes

Vue 3 has a new Global API, now we use createApp instead of new Vue({});
No more support for Filters, you should use computed proprieties or methods instead;
$on, $off, and $once methods are removed, you might have used them in the past alongside an eventBus;
data option should always be declared as a function;
defineAsyncComponent is the new method used to import and deal with async components;
Vue's Reactivity system is now based on ES2015 Proxies;

How to Create a new Vue 3 App

The most simple way is to just plug in a cdn script tag:

<html>
    <body>
     <div id="app">
       <p>{{ message }}</p>
     </div>
    <script src="https://unpkg.com/vue@next"></script>
    <script>
        const app = Vue.createApp({
          data() {
            return {
              message: 'I love Vue <3',
            }
          },
        })
        app.mount('#app')
    </script>
    </body>
</html>

You can start creating a fresh new Vue 3 App today quickly with the @vue/cli@4.5.0 to take advantage of a toon of integrations that Vue CLI provides out-of-the-box.

Alternatively, you can also use Vite, a blazing fast build tool for modern JavaScript Projects, it uses Browser Native ES Modules during development combined with Hot Module Replacement, with this approach your development server does not need to bundle all the files at once, but instead, it bundles only files you actually use at the time, which makes it also starts really fast and cold.

$ npm init @vitejs/app hello-vue3 --template vue
$ cd hello-vue3
$ npm i && npm run dev

You can learn more about Vite here.

New Global API

Previously in Vue 2.x apps, you would use new Vue() to create a root instance and pass a series of options.
Now with Vue 3.x, we have a new Global API for creating an app instance.

The idea is to place everything that mutates Vue's behavior at the level of the app instance.

// main.js

import { createApp } from 'vue';
import App from './App.vue';

// Create a Vue instance or app
const app = createApp(App)

app.use(/* vue router, vuex, ... */)
app.component(/* some global component... */)
app.directive(/* some custom directive... */)

app.mount('#app')

As you can see every configuration is scoped to a certain Vue application defined with createApp.

New Features

Composition API

This is definitely one of the game-changing ones, In fact, Composition API itself deserves a whole article about it, I'll do a quick overview of what it is and how it works.

You may be used to define a new component as an object with a set of options like data, methods, computed, and so on which is perfectly fine for small components, however as your app grows you end up creating complex and large components. Typically in these situations, we create Mixins to extract the common logic to be able to share with other components, which works in some cases but is not very flexible.

How composition works

Composition API allows us to reuse logic between components creating composable functions, so instead of having your logic split up in multiple component options, you can take advantage of composition functions to have all your logic code in one place.

In short, with this approach, our components are less complex and much more maintainable.

<template>
  ...
  <input
    type="search"
    v-model="searchInput"
    placeholder="Enter your favorite game..."
  />
  <button @click="fetchGame">
    Search
  </button>
  <ul v-if="games.results">
    <li v-for="game in games.results" :key="game.id">
      <GameCard :game="game" />
    </li>
  </ul>
  <p v-if="loading">Loading...</p>
  <p v-if="hasErrors">{{ hasErrors }}</p>
    ...
</template>

import { ref, computed, onMounted, onUnmounted } from 'vue';
import GameCard from '../components/GameCard.vue';
import useFetch from '../composables/useFetch';

export default {
  components: {
    GameCard,
  },
  // Pretty much everything lives inside this setup function
  setup() {
    const searchInput = ref('');
    const { results, hasErrors, loading, execute } = useFetch();

    // Executed when computed is mounted, similiar to Vue 2.x mounted lifecycle hook
    onMounted(() => {
      execute(
        'https://api.rawg.io/api/games?dates=2020-01-01,2020-12-31&ordering=-added'
      );
    });

    function fetchGame() {
      execute(`https://api.rawg.io/api/games?search=${searchInput.value}`);
    }

    // anything that needs to be accessed in the template
    return {
      searchInput,
      games: results,
      loading,
      hasErrors,
      execute,
      fetchGame,
    };
  },
};

First off, we're importing our components, methods and declaring our setup function.

As you can see we're not using the data() option, in this case, we use a ref. A ref is a reactive reference that allows us to track changes in the template.

We're using a composable function called useFetch to handle requests, and last but not least, we return our state.

Our composable function:

import { ref } from 'vue';

export default function useFetch {
  // reactive state
  const results = ref([]);
  const loading = ref(false);
  const hasErrors = ref(null);

  const execute = async url => {
    loading.value = true;

    try {
      const response = await fetch(url);
      const data = await response.json();
      results.value = data;
    } catch (err) {
      hasErrors.value = err;
    } finally {
      loading.value = false;
    }
  };

  return { results, loading, hasErrors, execute };
}

You can view this complete example in this repo.

Another good example of Composition API implementation is to create an IntersectionObserver composition function to lazy load images or components, for instance:

// useIntersection.js

import { ref } from 'vue';

export default function useIntersectionObserver() {
  const isSupported = 'IntersectionObserver' in window
  const isIntersecting = ref(false)
  const isShown = ref(false)

  if (!isSupported) {
    console.log('Your browser does not support this feature yet.')
  }

  const observer = new IntersectionObserver((entries) => {
    const component = entries[0]

    if (component.isIntersecting && !isShown.value) {
      isIntersecting.value = true
      isShown.value = true
    } else {
      isIntersecting.value = false
    }
  })

  const observe = (element) => {
    observer.observe(element)
  }

  const unobserve = (element) => {
    observer.unobserve(element)
  }

  return { observe, unobserve, isIntersecting, isShown }
}

Now in our component, we import it like a regular function and use the methods to dynamically render the image.
(Pretty similar to creating a custom hook in the React world).

<template>
  ...
  <div ref="el">
    <img :src="isShown ? game.background_image : null" />
  </div>
  ...
</template>

<script>
  import { ref, computed, onMounted, onUnmounted, onBeforeUnmount } from 'vue'
  import useIntersectionObserver from '../composables/useIntersectionObserver'

  export default {
    props: {
      game: Object,
    },
    setup(props, context) {
      const el = ref(null)
      const { observe, unobserve, isIntersecting } = useIntersectionObserver()

      onMounted(() => {
        observe(el.value)
      })

      onBeforeUnmount(() => {
        unobserve(el.value)
      })

      return { el, isIntersecting }
    },
  }
</script>

Benefits:

Code can now be organized by logical concerns (or features)
Keeps your components more readable
Extremely flexible

Good news: You can also use Composition API with *Vue 2 through @vue/composition api module!

It's good to say this syntax (setup) is optional, therefore you don't need to use composition for every single component you build, the standard object syntax is still completely valid.

Better TypeScript support

Vue 3 is completely written in TypeScript, which is good for everyone, now you can get better type definitions, develop more maintainable apps with typescript code, and, you can also get the Intellisense and Autocompletetion of your favorite code editor.

Suspense

Suspense is a native Vue component to deal with async dependencies. It is a good option to control what should render until a condition is met and our async component is ready.

In addition, it is a better way to handle multiple API calls from different components than relying on a v-if loading condition.

Note: Suspense is pretty experimental at this stage and its API might change in the future.

<template>
  <Suspense>
    <template #default>
      <GameList /> <!-- or Whatever async component you want to render -->
    </template>
    <template #fallback>
      Loading ...
    </template>
  </Suspense>
</template>

Teleport

We can use Teleport to write components that can have to move/teleport into different parts of your application, by selecting where (DOM element) to place even if this place is not where your app is mounted.

Teleport re-uses the DOM elements, so the state is preserved.

<div id="app"></div>
<div id="move-to-here"></div>
 
...
<template>
  <teleport to="#move-to-here">
    This should live outside of #app
  </teleport>
</template>

And you can select the target element in many ways

<teleport to="#id">
<teleport to=".class">
<teleport to="[data-modal]">

Simple, but very powerful!

Fragments

If you used React before you might know this one, in Vue 2.x we could not create a template with 2 elements at the same root and the reason for that is Vue instance that represents any Vue component needs to be bound into a single DOM element.

Now with Vue 3 you don't have to worry about that:

<!-- Before -->

<template>
    <div>
        <div>...<div>
        <div>...</div>
    </div>
</template>

<!-- After -->

<template>
    <div>...<div>
    <div>...</div>
</template>

Top comments (9)

Alexander B.K. • Nov 8 '20

Is Vue 3 officially released or still in Preview stage ?
I just started learning Vue, but when reading the doc, I now have to be aware of which version I read. I prefer Vue 3 with its new way of creating app instance as well as new features.
I like it incorporates refs and fragments that I have been familiar and used in React app.

Jeferson Brito • Nov 9 '20 • Edited

yes, it's officially released and currently on v3.0.2 now
The docs for Vue 3 are in v3.vuejs.org/

Others libraries like vue-router and vuex are still in beta
but you can start using them as well.

More details in github.com/vuejs/vue-next#supporti...

Alexander B.K. • Nov 9 '20

Thanks for reply
I have read Vue 3 doc, that's why my interest in learning Vue increased. But when I used Vue CLI for creating a simple, basic SPA, the CLI prompted presets option for Vue 3 like so : Vue 3 Preview.
So I thought Vue 3 was still in Preview stage.
However, now I don't care much for this, because I still want to try Vue 3 despite still in Preview stage.

mbokil • Sep 21 '20

The new Vue 3 is very nice. I have been testing it out and the performance is very nice. I have to wait though until they finish the IE11 compatibility since I have customers that need it. The composition API is excellent way to reuse code instead of messy mixins. It also simplifies writing larger components.