362 lines
7.3 KiB
Markdown
362 lines
7.3 KiB
Markdown
---
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title: Vue.js
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category: JavaScript
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updated: 2019-12-26
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weight: -10
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intro: |
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[Vue.js](https://vuejs.org/) is an open-source Model–view–viewmodel JavaScript framework for building user interfaces and single-page applications.
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---
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{%raw%}
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Expressions
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----------
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{: .-three-column}
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### Expressions
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```html
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<div id="app">
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<p>I have a {{ product }}</p>
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<p>{{ product + 's' }}</p>
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<p>{{ isWorking ? 'YES' : 'NO' }}</p>
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<p>{{ product.getSalePrice() }}</p>
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</div>
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```
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See: [Delimiters](https://vuejs.org/v2/api/#delimiters)
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### Binding
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```html
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<a v-bind:href="url">...</a>
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```
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#### Shorthand syntax
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```html
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<a :href="url">...</a>
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```
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{: data-line="1"}
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#### True or false will add or remove attribute
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```html
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<button :disabled="isButtonDisabled">...
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```
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#### If isActive is truthy, the class ‘active’ will appear
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```html
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<div :class="{ active: isActive }">...
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```
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#### Style color set to value of activeColor
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```html
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<div :style="{ color: activeColor }">
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```
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See: [v-bind](https://vuejs.org/v2/api/#v-bind)
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### Directives
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#### Element inserted/removed based on truthiness
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```html
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<p v-if="inStock">{{ product }}</p>
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```
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```html
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<p v-else-if="onSale">...</p>
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<p v-else>...</p>
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```
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#### Toggles the display: none CSS property
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```html
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<p v-show="showProductDetails">...</p>
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```
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#### Two-way data binding
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```html
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<input v-model="firstName" >
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```
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| Method | Description |
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| --- | --- |
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| `v-model.lazy="..."` | Syncs input after change event |
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| `v-model.number="..."` | Always returns a number |
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| `v-model.trim="..."` | Strips whitespace |
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See: [Directives](https://vuejs.org/v2/api/#Directives)
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### Actions/Events
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#### Calls addToCart method on component
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```html
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<button v-on:click="addToCart">...
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```
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#### Shorthand syntax
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```html
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<button @click="addToCart">...
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```
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{: data-line="1"}
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#### Arguments can be passed
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```html
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<button @click="addToCart(product)">...
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```
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#### To prevent default behavior (e.g. page reload)
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```html
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<form @submit.prevent="addProduct">...
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```
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#### Only trigger once
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```html
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<img @mouseover.once="showImage">...
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```
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| Method | Description |
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| --- | --- |
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| `.stop` | Stop all event propagation |
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| `.self ` | Only trigger if event.target is element itself |
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#### Keyboard entry example
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```html
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<input @keyup.enter="submit">
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```
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#### Call onCopy when control-c is pressed
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```html
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<input @keyup.ctrl.c="onCopy">
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```
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See: [Events](https://vuejs.org/v2/guide/events.html)
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### List rendering
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#### The `:key` is always recommended
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```html
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<li v-for="item in items"
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:key="item.id">
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{{ item }}
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</li>
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```
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{: data-line="2"}
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#### To access the position in the array
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```html
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<li v-for="(item, index) in items">...
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```
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#### To iterate through objects
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```html
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<li v-for="(value, key) in object">...
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```
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#### Using `v-for` with a component
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```html
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<cart-product v-for="item in products"
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:product="item"
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:key="item.id">
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```
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See: [List Rendering](https://vuejs.org/v2/guide/list.html)
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Component
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--------
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### Component anatomy
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```js
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Vue.component('my-component', {
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components: {
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// Components that can be used in the template
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ProductComponent,
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ReviewComponent
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},
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props: {
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// The parameters the component accepts
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message: String,
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product: Object,
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email: {
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type: String,
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required: true,
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default: "none"
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validator: function (value) {
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// Should return true if value is valid
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}
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}
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},
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data: function() {
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// `data` must be a function
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return {
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firstName: 'Vue',
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lastName: 'Mastery'
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}
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},
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computed: {
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// Return cached values until dependencies change
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fullName: function () {
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return this.firstName + ' ' + this.lastName
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}
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},
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watch: {
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// Called when firstName changes value
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firstName: function (value, oldValue) { ... }
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},
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methods: { ... },
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template: '<span>{{ message }}</span>',
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// Can also use backticks in `template` for multi-line
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})
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```
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{: data-line="3, 8, 16, 21, 28, 34, 39"}
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See: [Components Basics](https://vuejs.org/v2/guide/components.html)
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### Lifecycle hooks
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| Method | Description |
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| --- | --- |
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| `beforeCreate` | After the instance has been initialized [#](https://vuejs.org/v2/api/#beforeCreate) |
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| `created` | After the instance is created [#](https://vuejs.org/v2/api/#created) |
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| `beforeMount` | Before the first render [#](https://vuejs.org/v2/api/#beforeMount) |
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| `mounted` | After the instance has been mounted [#](https://vuejs.org/v2/api/#mounted) |
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| `beforeUpdate` | When data changes, before the DOM is patched [#](https://vuejs.org/v2/api/#beforeUpdate) |
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| `updated` | After a data change [#](https://vuejs.org/v2/api/#updated) |
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| `beforeDestroy` | Before the instance is destroyed [#](https://vuejs.org/v2/api/#beforeDestroy) |
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| `destroyed` | After a Vue instance has been destroyed [#](https://vuejs.org/v2/api/#destroyed) |
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See: [Lifecycle Hooks](https://vuejs.org/v2/api/#Options-Lifecycle-Hooks)
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### Custom events
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#### Set listener on component, within its parent
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```html
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<button-counter v-on:incrementBy="incWithVal">
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```
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#### Inside parent component
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```js
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methods: {
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incWithVal: function (toAdd) { ... }
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}
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```
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#### Inside button-counter template
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```js
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this.$emit(
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'incrementBy', // Custom event name
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5 // Data sent up to parent
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)
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```
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Use props to pass data into child components,
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custom events to pass data to parent elements.
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See: [Custom Events](https://vuejs.org/v2/guide/components-custom-events.html)
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Single file components
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--------
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### Single file
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```html
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<template>
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<p>{{ greeting }} World!</p>
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</template>
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<script>
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module.exports = {
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data: function () {
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return {
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greeting: 'Hello'
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}
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}
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}
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</script>
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<style scoped>
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p {
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font-size: 2em;
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text-align: center;
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}
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</style>
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```
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See: [Single File Components](https://vuejs.org/v2/guide/single-file-components.html)
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### Separation
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```html
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<template>
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<div>This will be pre-compiled</div>
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</template>
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<script src="./my-component.js"></script>
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<style src="./my-component.css"></style>
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```
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See: [What About Separation of Concerns?](https://vuejs.org/v2/guide/single-file-components.html#What-About-Separation-of-Concerns)
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Slots
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--------
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### Using a single slot
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#### Component template
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```html
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<div>
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<h2>I'm a title</h2>
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<slot>
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Only displayed if no slot content
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</slot>
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</div>
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```
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{: data-line="3,4,5"}
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#### Use of component with data for slot
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```html
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<my-component>
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<p>This will go in the slot</p>
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</my-component>
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```
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{: data-line="2"}
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See: [Slots](https://vuejs.org/v2/guide/components-slots.html)
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### Multiple slots
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#### Component template
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```html
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<div class="container">
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<header>
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<slot name="header"></slot>
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</header>
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<main>
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<slot>Default content</slot>
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</main>
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<footer>
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<slot name="footer"></slot>
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</footer>
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</div>
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```
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{: data-line="3,6,9"}
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#### Use of component with data for slots
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```html
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<app-layout>
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<h1 slot="header">Page title</h1>
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<p>the main content.</p>
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<p slot="footer">Contact info</p>
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</app-layout>
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```
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{: data-line="2,3,4"}
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See: [Slots](https://vuejs.org/v2/guide/components-slots.html)
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Also see
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--------
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* [Vue CLI](https://cli.vuejs.org/) _(cli.vuejs.org)_
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* [Vue Router](https://router.vuejs.org/) _(router.vuejs.org)_
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* [Vue DevTools](https://chrome.google.com/webstore/detail/vuejs-devtools/nhdogjmejiglipccpnnnanhbledajbpd?hl=en) _(chrome.google.com)_
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* [Nuxt.js](https://nuxtjs.org/) _(nuxtjs.org)_
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* [Vue.js v1.0.28 cheatsheet](vue@1.0.28/) _Legacy version_
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{%endraw%}
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