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

Table of contents

Breaking changes

  • Vue 3 has a new Global API, now we usecreateAppinstead ofnew Vue({})
  • No more support forFilters, you should usecomputed proprietiesor methods instead.
  • $on, $off, and $once methods are removed, you probably have used them before with aneventBus
  • dataoption should always be declared as a function
  • defineAsyncComponentis the new method used to import and deal with async components
  • Vue's Reactivity system is now based in 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

vue-cli

Alternatively, you can also useVite, 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 you only need to bundle the files you actually need and your dev server start fast and cold.

$ npm init vite-app hello-vue3
$ cd hello-vue3
$ npm i &amp;&amp; npm run dev

You can learn more about Vitehere.

New Global API

Previously in Vue 2.x apps, you would usenew 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 everything that mutates Vue's behavior should be placed 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 withcreateApp

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.

Composition API allows us to reuse logic between components creating composition functions, so instead of having your logic split up in multiple component options, you can take advantage of composition functions to have your 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,
  },
  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 thedata()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 returning 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 inthis repo.

Another good example of Composition API is to create aIntersectionObservercomposition function to lazy load our images like so:

// useIntersection.js

import { ref } from 'vue';

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

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

      if (component.isIntersecting) {
        isIntersecting.value = true;
      } else {
        isIntersecting.value = false;
      }
    });

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

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

    return { observe, unobserve, isIntersecting };
  } else {
    console.log('Your browser does not support this feature');
  }
}
<template>
	...
<div ref="el">
  <img
   :src="isIntersecting ? 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 { game } = props;
    const el = ref(null);
    const { observe, unobserve, isIntersecting } = useIntersectionObserver();

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

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

    return { game, 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 use Composition API with Vue 2 through@vue/composition api module

It's good to say this syntax 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 and, of course, you get theIntellisenseandAutocompletetionof 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 be moved/teleported into different parts of your application, by selecting where (DOM element) to place even if this place is not where your app is mounted.

alt Goku teleport

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>

Further reading

I'm very glad you reach until here and I hope you enjoyed reading 😊.

Here are some useful links to explore and learn more about Vue 3 🖖

Example shown in this post →https://github.com/jeferson-sb/demo-vue3

Vue 3.0 current status →https://github.com/vuejs/vue-next

Migration Guide →https://v3.vuejs.org/guide/migration/introduction.html#overview

Great collection of composable functions →https://github.com/pikax/vue-composable

https://vuedose.tips/go-async-in-vue-3-with-suspense/

https://vuedose.tips/easily-switch-to-composition-api-in-vuejs-3/

https://vueschool.io/articles/vuejs-tutorials/exciting-new-features-in-vue-3/