1
1
mirror of https://github.com/namibia/awesome-cheatsheets.git synced 2024-11-16 01:57:10 +00:00
awesome-cheatsheets/frontend/vue.js
2018-02-06 02:10:51 +00:00

800 lines
34 KiB
JavaScript
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

/* *******************************************************************************************
* GLOBAL CONFIG
* Vue.config is an object containing Vues global configurations.
* You can modify its properties listed below before bootstrapping your application.
* https://vuejs.org/v2/api/#Global-Config
* ******************************************************************************************* */
// Configure whether to allow vue-devtools inspection
Vue.config.devtools = true
// Enable component init, compile, render and patch performance tracing in the browser devtool timeline.
Vue.config.performance = true
// Prevent the production tip on Vue startup.
Vue.config.productionTip = false
// Suppress all Vue logs and warnings
Vue.config.silent = false
// Make Vue ignore custom elements defined outside of Vue
Vue.config.ignoredElements = [
'my-custom-web-component',
'another-web-component',
/^ion-/
]
// Define custom key alias(es) for v-on.
Vue.config.keyCodes = {
v: 86,
f1: 112,
// camelCase won`t work
mediaPlayPause: 179,
// instead you can use kebab-case with double quotation marks
"media-play-pause": 179,
up: [38, 87]
}
// Assign a handler for uncaught errors during component render function and watchers.
Vue.config.errorHandler = function (err, vm, info) {
// handle error
// `info` is a Vue-specific error info, e.g. which lifecycle hook
// the error was found in. Only available in 2.2.0+
}
// Define custom merging strategies for options
Vue.config.optionMergeStrategies._my_option = function (parent, child, vm) {
return child + 1
}
// Assign a custom handler for runtime Vue warnings.
// Note this only works during development and is ignored in production.
Vue.config.warnHandler = function (msg, vm, trace) {
// `trace` is the component hierarchy trace
}
/* *******************************************************************************************
* GLOBAL API
* https://vuejs.org/v2/api/#Global-API
* ******************************************************************************************* */
Vue.version // Provides the installed version of Vue as a string.
Vue.extend(options) // Create a “subclass” of the base Vue constructor.
Vue.mixin( mixin ) // Apply a mixin globally, which affects every Vue instance created afterwards.
Vue.nextTick([callback, context]) // Defer the callback to be executed after the next DOM update cycle.
Vue.use(plugin) // Install a Vue.js plugin. If the plugin is an Object, it must expose an install method.
Vue.set(target, key, value) // Set a property on an object. If the object is reactive, ensure the property is created as a reactive property and trigger view updates.
Vue.delete(target, key) // Delete a property on an object. If the object is reactive, ensure the deletion triggers view updates.
// Register or retrieve a global directive.
Vue.directive('my-directive', {
bind: function () {},
inserted: function () {},
update: function () {},
componentUpdated: function () {},
unbind: function () {}
})
// Register (function directive)
Vue.directive('my-directive', function () {
// This will be called as `bind` and `update`
})
// Getter, return the directive definition if registered
var myDirective = Vue.directive('my-directive')
// Register a global filter
Vue.filter('my-filter', function (value) { })
// Getter, return the filter if registered
var myFilter = Vue.filter('my-filter')
// Register an extended constructor
Vue.component('my-component', Vue.extend({ }))
// Register an options object (automatically call Vue.extend)
Vue.component('my-component', { })
// Retrieve a registered component (always return constructor)
var MyComponent = Vue.component('my-component')
Vue.compile(template) // Compiles a template string into a render function
/* *******************************************************************************************
* OPTIONS > DATA
* https://vuejs.org/v2/api/#Options-Data
* ******************************************************************************************* */
new Vue({
// A list/hash of attributes that are exposed to accept data from the parent component.
// It has an Array-based simple syntax and an alternative Object-based syntax that allows
// advanced configurations such as type checking, custom validation and default values.
props: {
height: Number,
age: {
type: Number,
default: 0,
required: true,
validator: function (value) {
return value >= 0
}
}
},
// Primarily intended to make unit testing easier
propsData: {
age: 12
},
// The data object for the Vue instance.
// Vue will recursively convert its properties into getter/setters to make it “reactive”.
// Note: you should not use an arrow function with the data property
data () {
return {
a: 1,
b: 2
}
},
// Computed properties to be mixed into the Vue instance.
// All getters and setters have their this context automatically bound to the Vue instance.
// Computed properties are cached, and only re-computed on reactive dependency changes.
// Note that if a certain dependency is out of the instances scope (i.e. not reactive),
// the computed property will not be updated.
computed: {
// Note: you should not use an arrow function to define a computed property.
aDouble: function () {
return this.a * 2
},
aPlus: {
get: function () {
return this.a + 1
},
set: function (v) {
this.a = v - 1
}
}
},
// An object where keys are expressions to watch and values are the corresponding callbacks.
// The value can also be a string of a method name, or an Object that contains additional options.
// The Vue instance will call $watch() for each entry in the object at instantiation.
watch: {
// Note: you should not use an arrow function to define a watcher.
a: function (val, oldVal) {
console.log('new: %s, old: %s', val, oldVal)
},
// String method name
b: 'someMethod',
// Deep watcher
c: {
handler: function (val, oldVal) { /* ... */ },
deep: true
},
// The callback will be called immediately after the start of the observation
d: {
handler: function (val, oldVal) { /* ... */ },
immediate: true
}
},
// Methods to be mixed into the Vue instance. You can access these methods directly on the VM instance,
// or use them in directive expressions. All methods will have their this context automatically bound to
// the Vue instance.
methods: {
// Note: you should not use an arrow function to define a method.
plus () {
this.a++
}
}
})
/* *******************************************************************************************
* OPTIONS > DOM
* https://vuejs.org/v2/api/#Options-DOM
* ******************************************************************************************* */
new Vue({
// Provide the Vue instance an existing DOM element to mount on.
// It can be a CSS selector string or an actual HTMLElement.
// After the instance is mounted, the resolved element will be accessible as vm.$el.
el: '#example',
// A string template to be used as the markup for the Vue instance.
// The template will replace the mounted element.
// Any existing markup inside the mounted element will be ignored,
// unless content distribution slots are present in the template.
// If the string starts with # it will be used as a querySelector and
// use the selected elements innerHTML as the template string. This
// allows the use of the common <script type="x-template"> trick to include templates.
template: `
<div class="checkbox-wrapper" @click="check">
<div :class="{ checkbox: true, checked: checked }"></div>
<div class="title">{{ title }}</div>
</div>
`,
// An alternative to string templates allowing you to leverage the full programmatic power of JavaScript.
// The render function receives a createElement method as its first argument used to create VNodes.
// If the component is a functional component, the render function also receives an extra argument context,
// which provides access to contextual data since functional components are instance-less.
render (createElement) {
// create kebabCase id
var headingId = getChildrenTextContent(this.$slots.default)
.toLowerCase()
.replace(/\W+/g, '-')
.replace(/(^\-|\-$)/g, '')
return createElement(
'h' + this.level,
[
createElement('a', {
attrs: {
name: headingId,
href: '#' + headingId
}
}, this.$slots.default)
]
)
},
// Provide an alternative render output when the default render function encounters an error.
// The error will be passed to renderError as the second argument.
// This is particularly useful when used together with hot-reload.
renderError (createElement, err) {
return createElement('pre', { style: { color: 'red' }}, err.stack)
}
})
/* *******************************************************************************************
* OPTIONS > LIFECYCLE HOOKS
* https://vuejs.org/v2/api/#Options-Lifecycle-Hooks
* ******************************************************************************************* */
// All lifecycle hooks automatically have their this context bound to the instance,
// so that you can access data, computed properties, and methods. This means you should not
// use an arrow function to define a lifecycle method (e.g. created: () => this.fetchTodos()).
// The reason is arrow functions bind the parent context, so this will not be the Vue instance as
// you expect and this.fetchTodos will be undefined.
new Vue({
// Called synchronously immediately after the instance has been initialized,
// before data observation and event/watcher setup.
beforeCreate () {
console.log('The instance has been initialized')
},
// Called synchronously after the instance is created. At this stage, the instance has
// finished processing the options which means the following have been set up: data observation,
// computed properties, methods, watch/event callbacks. However, the mounting phase has not been
// started, and the $el property will not be available yet.
created () {
console.log('The instance has been created')
},
// Called right before the mounting begins: the render function
// is about to be called for the first time.
beforeMount () {
console.log('The instance is about to be mounted')
},
// Called after the instance has been mounted, where el is replaced by the newly created vm.$el.
// If the root instance is mounted to an in-document element, vm.$el will also be in-document when
// mounted is called.
mounted () {
console.log('The instance has been mounted')
// Note that mounted does not guarantee that all child components have also been mounted.
// If you want to wait until the entire view has been rendered, you can use vm.$nextTick
// inside of mounted:
this.$nextTick(function () {
// Code that will run only after the
// entire view has been rendered
})
},
// Called when the data changes, before the virtual DOM is re-rendered and patched.
// You can perform further state changes in this hook and they will not trigger additional re-renders.
// This hook is not called during server-side rendering.
beforeUpdate () {
console.log('The instance is about to be re-rendered and patched')
},
// The components DOM will have been updated when this hook is called, so you can perform DOM-dependent
// operations here. However, in most cases you should avoid changing state inside the hook. To react
// to state changes, its usually better to use a computed property or watcher instead.
updated () {
console.log('The instance has been re-rendered and patched')
// Note that updated does not guarantee that all child components have also been re-rendered.
// If you want to wait until the entire view has been re-rendered, you can use vm.$nextTick
// inside of updated:
this.$nextTick(function () {
// Code that will run only after the
// entire view has been re-rendered
})
},
// Called when a kept-alive component is activated.
activated () {
console.log('Component activated')
},
// Called when a kept-alive component is deactivated.
deactivated () {
console.log('Component deactivated')
},
// Called right before a Vue instance is destroyed.
// At this stage the instance is still fully functional.
beforeDestroy () {
console.log('The instance is about to be destroyed')
},
// Called after a Vue instance has been destroyed.
// When this hook is called, all directives of the Vue instance have been unbound,
// all event listeners have been removed, and all child Vue instances have also been destroyed.
destroyed () {
console.log('The instance has been destroyed')
},
// Called when an error from any descendent component is captured.
// The hook receives three arguments: the error, the component instance that triggered the error,
// and a string containing information on where the error was captured.
// The hook can return false to stop the error from propagating further.
errorCaptured (error, vm, info) {
console.log(`The error (${error}) has been captured for ${vm}: ${info}`)
// An errorCaptured hook can return false to prevent the error from propagating further.
// This is essentially saying “this error has been handled and should be ignored.”
// It will prevent any additional errorCaptured hooks or the global config.errorHandler
// from being invoked for this error.
return false
},
})
/* *******************************************************************************************
* OPTIONS > ASSETS
* https://vuejs.org/v2/api/#Options-Assets
* ******************************************************************************************* */
new Vue({
// A hash of directives to be made available to the Vue instance.
directives: {
myDirective: {
// Called only once, when the directive is first bound to the element.
// This is where you can do one-time setup work.
bind: function (el, binding, vnode, oldVnode) {
console.log('The directive is first bound to the element.')
},
// Called when the bound element has been inserted into its parent node
// (this only guarantees parent node presence, not necessarily in-document).
inserted: function (el, binding, vnode, oldVnode) {
console.log('The bound element has been inserted into its parent node.')
},
// Called after the containing components VNode has updated, but possibly before its
// children have updated. The directives value may or may not have changed, but you can
// skip unnecessary updates by comparing the bindings current and old values (see below
// on hook arguments).
update: function (el, binding, vnode, oldVnode) {
console.log('The component VNode has updated.')
},
// Called after the containing components VNode and the VNodes of its children have updated.
componentUpdated: function (el, binding, vnode, oldVnode) {
console.log('The components VNode and the VNodes of its children have updated.')
},
// Called only once, when the directive is unbound from the element.
unbind: function (el, binding, vnode, oldVnode) {
console.log('The directive is unbound from the element.')
},
}
},
// A hash of filters to be made available to the Vue instance.
filters: {
myFilter: function (value) {
console.log('Do your computations and return something to display.')
}
}
})
/* *******************************************************************************************
* OPTIONS > COMPOSITION
* https://vuejs.org/v2/api/#Options-Composition
* ******************************************************************************************* */
new Vue({
// Specify the parent instance for the instance to be created. Establishes a parent-child
// relationship between the two. The parent will be accessible as this.$parent for the child,
// and the child will be pushed into the parents $children array.
parent: vueInstance,
// The mixins option accepts an array of mixin objects. These mixin objects can contain instance
// options like normal instance objects, and they will be merged against the eventual options
// using the same option merging logic in Vue.extend(). e.g. If your mixin contains a created
// hook and the component itself also has one, both functions will be called.
// Mixin hooks are called in the order they are provided, and called before the components own hooks.
mixins: [mixin],
// Allows declaratively extending another component (could be either a plain options object or a
// constructor) without having to use Vue.extend. This is primarily intended to make it easier to
// extend between single file components. This is similar to mixins, the difference being that
// the components own options takes higher priority than the source component being extended.
extends: ObjectOrFunction,
})
/* *******************************************************************************************
* OPTIONS > MISC
* https://vuejs.org/v2/api/#Options-Lifecycle-Hooks
* ******************************************************************************************* */
new Vue({
// Allow the component to recursively invoke itself in its template.
// Note that when a component is registered globally with Vue.component(), the global ID is
// automatically set as its name.
// Another benefit of specifying a name option is debugging. Named components result in more
// helpful warning messages. Also, when inspecting an app in the vue-devtools, unnamed components
// will show up as <AnonymousComponent>, which isnt very informative. By providing the name
// option, you will get a much more informative component tree.
name: 'myComponent',
// Change the plain text interpolation delimiters.
delimiters: ['${', '}'],
// Causes a component to be stateless (no data) and instanceless (no this context). They are
// only a render function that returns virtual nodes making them much cheaper to render.
functional: true,
// By default, parent scope attribute bindings that are not recognized as props will
// “fallthrough” and be applied to the root element of the child component as normal HTML
// attributes. When authoring a component that wraps a target element or another component,
// this may not always be the desired behavior. By setting inheritAttrs to false, this default
// behavior can be disabled. The attributes are available via the $attrs instance property
// (also new in 2.4) and can be explicitly bound to a non-root element using v-bind.
// Note: this option does not affect class and style bindings.
inheritAttrs: true,
// When set to true, will preserve and render HTML comments found in templates. The default
// behavior is discarding them.
comments: true,
})
/* *******************************************************************************************
* INSTANCE PROPERTIES
* https://vuejs.org/v2/api/#Instance-Properties
* ******************************************************************************************* */
// The data object that the Vue instance is observing.
// The Vue instance proxies access to the properties on its data object.
vm.$data
// An object representing the current props a component has received.
// The Vue instance proxies access to the properties on its props object.
vm.$props
// The root DOM element that the Vue instance is managing.
vm.$el
// The instantiation options used for the current Vue instance.
// This is useful when you want to include custom properties in the options:
vm.$options
// The parent instance, if the current instance has one.
vm.$parent
// The root Vue instance of the current component tree.
// If the current instance has no parents this value will be itself.
vm.$root
// The direct child components of the current instance.
// Note theres no order guarantee for $children, and it is not reactive.
// If you find yourself trying to use $children for data binding,
// consider using an Array and v-for to generate child components,
// and use the Array as the source of truth.
vm.$children
// Used to programmatically access content distributed by slots.
// Each named slot has its own corresponding property (e.g. the contents of slot="foo" will
// be found at vm.$slots.foo). The default property contains any nodes not included in a named slot.
// Accessing vm.$slots is most useful when writing a component with a render function.
vm.$slots
// Used to programmatically access scoped slots. For each slot, including the default one, the
// object contains a corresponding function that returns VNodes.
// Accessing vm.$scopedSlots is most useful when writing a component with a render function.
vm.$scopedSlots
// An object that holds child components that have ref registered.
vm.$refs
// Whether the current Vue instance is running on the server.
vm.$isServer
// Contains parent-scope attribute bindings (except for class and style) that are not recognized
// (and extracted) as props. When a component doesnt have any declared props, this essentially
// contains all parent-scope bindings (except for class and style), and can be passed down to an
// inner component via v-bind="$attrs" - useful when creating higher-order components.
vm.$attrs
// Contains parent-scope v-on event listeners (without .native modifiers).
// This can be passed down to an inner component via v-on="$listeners" - useful when creating
// higher-order components.
vm.$listeners
/* *******************************************************************************************
* INSTANCE METHODS > DATA
* https://vuejs.org/v2/api/#Instance-Methods-Data
* ******************************************************************************************* */
// Watch an expression or a computed function on the Vue instance for changes.
// The callback gets called with the new value and the old value.
// The expression only accepts dot-delimited paths.
// For more complex expressions, use a function instead.
var unwatch = vm.$watch('a.b.c', function (newVal, oldVal) {
// do something
}, {
// To also detect nested value changes inside Objects, you need to pass in deep: true
// in the options argument. Note that you dont need to do so to listen for Array mutations.
deep: true,
// Passing in immediate: true in the option will trigger the callback immediately with the
// current value of the expression:
immediate: true
})
// later, teardown the watcher
unwatch()
// This is the alias of the global Vue.set.
vm.$set(target,key, value)
// This is the alias of the global Vue.delete.
vm.$delete(target, key)
/* *******************************************************************************************
* INSTANCE METHODS > EVENTS
* https://vuejs.org/v2/api/#Instance-Methods-Events
* ******************************************************************************************* */
// Listen for a custom event on the current vm. Events can be triggered by vm.$emit.
// The callback will receive all the additional arguments passed into these event-triggering methods.
vm.$on(event, callback)
// Listen for a custom event, but only once.
// The listener will be removed once it triggers for the first time.
vm.$once(event, callback)
// Remove custom event listener(s).
// If no arguments are provided, remove all event listeners;
// If only the event is provided, remove all listeners for that event;
// If both event and callback are given, remove the listener for that specific callback only.
vm.$off([event, callback])
// Trigger an event on the current instance.
// Any additional arguments will be passed into the listeners callback function.
vm.$emit(event, [args])
/* *******************************************************************************************
* INSTANCE METHODS > LIFECYCLE
* https://vuejs.org/v2/api/#Instance-Methods-Lifecycle
* ******************************************************************************************* */
// If a Vue instance didnt receive the el option at instantiation, it will be in “unmounted”
// state, without an associated DOM element. vm.$mount() can be used to manually start the mounting
// of an unmounted Vue instance.
vm.$mount([elementOrSelector])
// Force the Vue instance to re-render. Note it does not affect all child components,
// only the instance itself and child components with inserted slot content.
vm.$forceUpdate()
// Defer the callback to be executed after the next DOM update cycle.
// Use it immediately after youve changed some data to wait for the DOM update.
// This is the same as the global Vue.nextTick, except that the callbacks this context is
// automatically bound to the instance calling this method.
vm.$nextTick([callback])
// Completely destroy a vm. Clean up its connections with other existing vms, unbind all its
// directives, turn off all event listeners.
// Triggers the beforeDestroy and destroyed hooks.
vm.$destroy()
/* *******************************************************************************************
* DIRECTIVES
* https://vuejs.org/v2/api/#Directives
* ******************************************************************************************* */
// <!-- Updates the elements textContent. -->
// <!-- If you need to update the part of textContent, you should use {{ Mustache }} interpolations. -->
// <span v-text="msg"></span>
// <!-- Updates the elements innerHTML. Note that the contents are inserted as plain HTML -->
// <!-- they will not be compiled as Vue templates. If you find yourself trying to compose templates -->
// <!-- using v-html, try to rethink the solution by using components instead. -->
// <div v-html="html"></div>
// <!-- Toggles the elements display CSS property based on the truthy-ness of the expression value. -->
// <!-- This directive triggers transitions when its condition changes. -->
// <div v-show="condition"></div>
// <!-- Conditionally render the element based on the truthy-ness of the expression value. -->
// <!-- The element and its contained directives / components are destroyed and re-constructed -->
// <!-- during toggles. If the element is a <template> element, its content will be extracted as -->
// <!-- the conditional block. This directive triggers transitions when its condition changes. -->
// <div v-if="condition"></div>
// <div v-else-if="anotherCondition"></div>
// <div v-else></div>
// <!-- Render the element or template block multiple times based on the source data. -->
// <!-- The directives value must use the special syntax alias in expression to provide an alias -->
// <!-- for the current element being iterated on: -->
// <div v-for="item in items">{{ item.text }}</div>
// <!-- Alternatively, you can also specify an alias for the index (or the key if used on an Object): -->
// <div v-for="(item, index) in items"></div>
// <div v-for="(val, key) in object"></div>
// <div v-for="(val, key, index) in object"></div>
// <!-- Attaches an event listener to the element. The event type is denoted by the argument. -->
// <!-- The expression can be a method name, an inline statement, or omitted if there are modifiers present. -->
// .stop: Call event.stopPropagation().
// .prevent: Call event.preventDefault().
// .capture: Add event listener in capture mode.
// .self: Only trigger handler if event was dispatched from this element.
// .{keyCode | keyAlias}: Only trigger handler on certain keys.
// .native: Listen for a native event on the root element of component.
// .once: Trigger handler at most once.
// .left: (2.2.0+) only trigger handler for left button mouse events.
// .right: (2.2.0+) only trigger handler for right button mouse events.
// .middle: (2.2.0+) only trigger handler for middle button mouse events.
// .passive: (2.3.0+) attaches a DOM event with { passive: true }.
// Method handler: <button v-on:click="doThis"></button>
// Object syntax (2.4.0+): <button v-on="{ mousedown: onMouseDown, mouseup: onMouseUp }"></button>
// Inline statement: <button v-on:click="doThat('hello', $event)"></button>
// Shorthand: <button @click="doThis"></button>
// Stop propagation: <button @click.stop="doThis"></button>
// Prevent default: <button @click.prevent="doThis"></button>
// Prevent default without expression: <form @submit.prevent></form>
// Chain modifiers: <button @click.stop.prevent="doThis"></button>
// Key modifier using keyAlias: <input @keyup.enter="onEnter">
// Key modifier using keyCode: <input @keyup.13="onEnter">
// The click event will be triggered at most once: <button v-on:click.once="doThis"></button>
// <!-- Dynamically bind one or more attributes, or a component prop to an expression. -->
// <!-- When used to bind the class or style attribute, it supports additional value types such as -->
// <!-- Array or Objects. See linked guide section below for more details. -->
// .prop: Bind as a DOM property instead of an attribute.
// .camel: (2.1.0+) transform the kebab-case attribute name into camelCase.
// .sync: (2.3.0+) a syntax sugar that expands into a v-on handler for updating the bound value.
// Bind an attribute: <img v-bind:src="imageSrc">
// Shorthand: <img :src="imageSrc">
// With inline string concatenation: <img :src="'/path/to/images/' + fileName">
// Class binding: <div :class="{ red: isRed }"></div>
// Style binding: <div :style="{ fontSize: size + 'px' }"></div>
// Binding an object of attributes <div v-bind="{ id: someProp, 'other-attr': otherProp }"></div>
// DOM attribute binding with prop modifier: <div v-bind:text-content.prop="text"></div>
// Prop binding. "prop" must be declared in my-component: <my-component :prop="someThing"></my-component>
// Pass down parent props in common with a child component: <child-component v-bind="$props"></child-component>
// XLink: <svg><a :xlink:special="foo"></a></svg>
// <!-- Create a two-way binding on a form input element or a component. -->
// <!-- For detailed usage and other notes, see the Guide section linked below. -->
// .lazy: Listen to change events instead of input
// .number: Cast input string to numbers
// .trim: Trim input
// <input v-model="message" placeholder="edit me">
// <textarea v-model="message" placeholder="add multiple lines"></textarea>
// <input type="checkbox" id="checkbox" v-model="checked">
// <!-- Skip compilation for this element and all its children. -->
// <!-- You can use this for displaying raw mustache tags. -->
// <!-- Skipping large numbers of nodes with no directives on them can also speed up compilation. -->
// <span v-pre>{{ this will not be compiled }}</span>
// <!-- This directive will remain on the element until the associated Vue instance finishes -->
// <!-- compilation. Combined with CSS rules such as [v-cloak] { display: none }, this directive -->
// <!-- can be used to hide un-compiled mustache bindings until the Vue instance is ready. -->
// <div v-cloak>{{ message }}</div>
// [v-cloak] { display: none; }
// <!-- Render the element and component once only. On subsequent re-renders, the element/component -->
// <!-- and all its children will be treated as static content and skipped. This can be used to -->
// <!-- optimize update performance. -->
// <span v-once>This will never change: {{msg}}</span>
// <my-component v-once :comment="msg"></my-component>
/* *******************************************************************************************
* SPECIAL ATTRIBUTES
* https://vuejs.org/v2/api/#Special-Attributes
* ******************************************************************************************* */
// <!-- The key special attribute is primarily used as a hint for Vues virtual DOM algorithm to -->
// <!-- identify VNodes when diffing the new list of nodes against the old list. Without keys, Vue uses -->
// <!-- an algorithm that minimizes element movement and tries to patch/reuse elements of the same type -->
// <!-- in-place as much as possible. With keys, it will reorder elements based on the order change of -->
// <!-- keys, and elements with keys that are no longer present will always be removed/destroyed. -->
// <ul><li v-for="item in items" :key="item.id">...</li></ul>
// <transition><span :key="text">{{ text }}</span></transition>
// <!-- ref is used to register a reference to an element or a child component. The reference will be -->
// <!-- registered under the parent components $refs object. If used on a plain DOM element, the -->
// <!-- reference will be that element; if used on a child component, the reference will be component instance: -->
// <!-- vm.$refs.p will be the DOM node -->
// <p ref="p">hello</p>
// <!-- vm.$refs.child will be the child comp instance -->
// <child-comp ref="child"></child-comp>
// <!-- Used on content inserted into child components to indicate which named slot the content belongs to. -->
// <!-- Child markup: -->
// <header><slot name="header"></slot></header>
// <!-- Parent markup: -->
// <app-layout><h1 slot="header">Here might be a page title</h1></app-layout>
// <!-- Used for dynamic components and to work around limitations of in-DOM templates. -->
// <component :is="currentView"></component>