Vue.Js - Programmer Sheet

Vue.Js - Programmer Sheet

Expressions

<div id="app">
  <p>I have a {{ product }}</p>
  <p>{{ product + 's' }}</p>
  <p>{{ isWorking ? 'YES' : 'NO' }}</p>
  <p>{{ product.getSalePrice() }}</p>
</div>

Directives

Element inserted/removed based on truthiness

<p v-if="inStock">{{ product }}</p> 
<p v-else>...</p>

Toggles the display: none CSS property

<p v-show="showProductDetails">...</p>

Two-way data binding

<input v-model="firstName" >

v-model.lazy="..."
 //Syncs input after change event

v-model.number="..."  
//Always returns a number

v-model.trim="..."   
//Strips whitespace

Actions/Events

Calls addToCart method on component

<button v-on:click="addToCart">...

Shorthand syntax

<button @click="addToCart">...

Arguments can be passed

<button @click="addToCart(product)">...

To prevent default behavior (e.g. page reload)

<form @submit.prevent="addProduct">...

Only trigger once

<img @mouseover.once="showImage">...

.stop   
  //Stop all event propagation

.self   
//Only trigger if event.target is element itself

Keyboard entry example

<input @keyup.enter="submit">

Call onCopy when control-c is pressed

<input @keyup.ctrl.c="onCopy">

List rendering

The :key is always recommended

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

To access the position in the array

<li v-for="(item, index) in items">...

To iterate through objects

<li v-for="(value, key) in object">...

Using v-for with a component

<cart-product v-for="item in products"
  :product="item"
  key="item.id">

Binding

<a v-bind:href="url">...</a>

Shorthand syntax

<a :href="url">...</a>

True or false will add or remove attribute

<button :disabled="isButtonDisabled">...

If isActive is truthy, the class ‘active’ will appear

<div :class="{ active: isActive }">...

Style color set to value of activeColor

<div :style="{ color: activeColor }">

Component anatomy

Vue.component('my-component', {
  components: {
    // Components that can be used in the template
    ProductComponent,
    ReviewComponent
  },
  props: {
    // The parameters the component accepts
    message: String,
    product: Object,
    email: {
      type: String,
      required: true,
      default: "none"
      validator: function (value) {
        // Should return true if value is valid
      }
    }
  },
  data: function() {
    // `data` must be a function
    return {
      firstName: 'Vue',
      lastName: 'Mastery'
    }
  },
  computed: {
    // Return cached values until dependencies change
    fullName: function () {
      return this.firstName + ' ' + this.lastName
    }
  },
  watch: {
    // Called when firstName changes value
    firstName: function (value, oldValue) { ... }
  },
  methods: { ... },
  template: '<span>{{ message }}</span>',
  // Can also use backticks in `template` for multi-line
})

Lifecycle hooks

beforeCreate	After the instance has been initialized #
created	After the instance is created #
beforeMount	Before the first render #
mounted	After the instance has been mounted #
beforeUpdate	When data changes, before the DOM is patched #
updated	After a data change #
beforeDestroy	Before the instance is destroyed #
destroyed	After a Vue instance has been destroyed #

Custom events

Set listener on component, within its parent

<button-counter v-on:incrementBy="incWithVal">

Inside parent component

methods: {
  incWithVal: function (toAdd) { ... }
}

Inside button-counter template

this.$emit(
  'incrementBy', // Custom event name
  5 // Data sent up to parent
)

Use props to pass data into child components, custom events to pass data to parent elements.

Single file

<template>
  <p>{{ greeting }} World!</p>
</template>

<script>
module.exports = {
  data: function () {
    return {
      greeting: 'Hello'
    }
  }
}
</script>

<style scoped>
p {
  font-size: 2em;
  text-align: center;
}
</style>

Separation

<template>
  <div>This will be pre-compiled</div>
</template>
<script src="./my-component.js"></script>
<style src="./my-component.css"></style>

Using a single slot

Component template

<div>
  <h2>I'm a title</h2>
  <slot>
    Only displayed if no slot content
  </slot>
</div>

Use of component with data for slot

<my-component>
  <p>This will go in the slot</p>
</my-component>

Multiple slots

Component template

<div class="container">
  <header>
    <slot name="header"></slot>
  </header>
  <main>
    <slot>Default content</slot>
  </main>
  <footer>
    <slot name="footer"></slot>
  </footer>
</div>

Use of component with data for slots

<app-layout>
  <h1 slot="header">Page title</h1>
  <p>the main content.</p>
  <p slot="footer">Contact info</p>
</app-layout>