Starting with Vue 3

Vue Mastery intro course

Post created on: 11/29/2020

I bought myself a year-long subscription to Vue Mastery in the Black Friday Sale and although I know some Vue (version 2) I'm keen to learn more and also see the differences between Vue 2 and Vue 3.

As a starting point today I have completed the Intro to Vue 3 course on the site and much of the syntax appears to be the same, but there are a few differences. For example, initialising a basic Vue app after setting up and a basic index.html page and importing Vue through the CDN as its the quickest way to get started

// Vue 2

const app = new Vue({
  el: '#app',
  data: {
   name: 'Jane'

// Vue 3

const app = Vue.createApp({
    return {
      name: 'Jane'

Once this is set up you need to import and 'mount' the app to the DOM e.g.

const mountedApp = app.mount('#app')

Attribute Binding

This dynamically binds an attribute to an expression e.g.

<a v-bind href="url">My Website</a>
  return {
    url: ''

Shorthand for this is simple :

Conditional Rendering

This is done using a Vue directive called v-if this can be used with v-else or on its own e.g.

<p v-if="inStock">Product is in stock</p>
<p v-else>Out of stock</p>

You can also chain logic using v-if/v-else-if/v-else like a standard js if-else conditional.

Another option is to use v-show this is different because instead of removing the element from the DOM as v-if does instead it toggles the visibility. This is the better option for performance if you have an element that changes often.

List Rendering

This uses v-for directive and it works like a classic for loop in javascript e.g.

<li v-for="items in items" :key="">{{ item }}</li>

MAke asure to add a key to give each element a unique key for Vue to be able to keep track of them.

Event Handling

You listen for events using the v-on directive and its event type e.g. click, mouseover(equivalent to hover)

<button v-on:click="dosomething">
// using shorthand
<button @click="doSomething">

A simple example would be adding values to keep score or add values to a cart e.g.

<button @click="addToScore">
methods: {
    this.score += 1

Class and Style Binding

Dynamically binding classes and styles work the same way as other attributes except you use either the object or array syntax e.g."{ backgroundColor: option.color }"

It is important to note anything in {} is read as JavaScript, therefore, you need to use either camelCase or kebab-case but be sure to use quotes if you using kebab-case e.g.:style="{ 'background-color': 'red' }"

If you are using multiple styles you could bind to an object e.g. <p :style="myStyles">Some random text</p>

  return {
    myStyles: {
      color: 'red',
      font-size: 1rem,

You can also conditionally bind classes to elements e.g.

<button :class="{ CSSClass: !inStock } :disabled="!inStock">Text here</button>

Computed Properties

These calculate values and are useful because they cache these values and will only update when one of the dependencies change e.g.

computed: {
    return this.myName +  ' ' + this.myProduct
    if(this.onSale) {
      return this.myName + ' ' + this.myProduct + ' is on sale!'
      return ' '

Components and Props

Components are the building blocks of Vue apps that are reusable. When creating an example the structure is as follows:

app.component('component-name', {
  props: (to pass values),
  template: `` (add html here),
  methods: {},

In most cases, you will use Single File Components (SFCs) which are what is created when using the Vue-CLI to scaffold an app.

Communicating Events

This is useful when passing values from child components up to the parent. This is done by emitting a custom event e.g. this.$emit('event-name') which is then referenced in your component e.g. <my-component @event-name="doSomething">

Forms and v-model

Two way data binding with v-model - set properties in data and then in HTML add v-model="name" or v-model.number="rating".

Form input modifiers

.number is a modifier to type check that the value is a number. The only form input bindings are .lazy to only sync after change events and .trim which will remove any whitespace.

Another useful example is .prevent e.g. on form @submit.prevent="onSubmitMethod" as the name suggests this is like using event.preventDefault in standard JS to prevent the browser reloading the page on submission of a form.