Vue Component Registration

https://vuejs.org/v2/guide/components-registration.html

Global Registration

So far, we’ve only created components using Vue.component:

Vue.component('my-component-name', {
  // ... options ...
})

These components are globally registered. That means they can be used in the template of any root Vue instance (new Vue) created after registration. For example:

Vue.component('component-a', { /* ... */ })
Vue.component('component-b', { /* ... */ })
Vue.component('component-c', { /* ... */ })

new Vue({ el: '#app' })

<div id="app">
  <component-a></component-a>
  <component-b></component-b>
  <component-c></component-c>
</div>

This even applies to all subcomponents, meaning all three of these components will also be available inside each other.

Local Registration

Global registration often isn’t ideal. For example, if you’re using a build system like Webpack, globally registering all components means that even if you stop using a component, it could still be included in your final build. This unnecessarily increases the amount of JavaScript your users have to download.

In these cases, you can define your components as plain JavaScript objects:

var ComponentA = { /* ... */ }
var ComponentB = { /* ... */ }
var ComponentC = { /* ... */ }

Then define the components you’d like to use in a components option:

new Vue({
  el: '#app',
  components: {
    'component-a': ComponentA,
    'component-b': ComponentB
  }
})

For each property in the components object, the key will be the name of the custom element, while the value will contain the options object for the component.

Note that locally registered components are not also available in subcomponents. For example, if you wanted ComponentA to be available in ComponentB, you’d have to use:

var ComponentA = { /* ... */ }

var ComponentB = {
  components: {
    'component-a': ComponentA
  },
  // ...
}

Or if you’re using ES2015 modules, such as through Babel and Webpack, that might look more like:

import ComponentA from './ComponentA.vue'

export default {
  components: {
    ComponentA
  },
  // ...
}

Note that in ES2015+, placing a variable name like ComponentA inside an object is shorthand for ComponentA: ComponentA, meaning the name of the variable is both:

• the custom element name to use in the template, and
• the name of the variable containing the component options

Module Systems

If you’re not using a module system with import/require, you can probably skip this section for now. If you are, we have some special instructions and tips just for you.

Local Registration in a Module System

If you’re still here, then it’s likely you’re using a module system, such as with Babel and Webpack. In these cases, we recommend creating a components directory, with each component in its own file.

Then you’ll need to import each component you’d like to use, before you locally register it. For example, in a hypothetical假设的 ComponentB.js or ComponentB.vue file:

import ComponentA from './ComponentA'
import ComponentC from './ComponentC'

export default {
  components: {
    ComponentA,
    ComponentC
  },
  // ...
}

Now both ComponentA and ComponentC can be used inside ComponentB‘s template.

Automatic Global Registration of Base Components

Many of your components will be relatively generic, possibly only wrapping an element like an input or a button. We sometimes refer to these as base components and they tend to be used very frequently across your components.

The result is that many components may include long lists of base components:

import BaseButton from './BaseButton.vue'
import BaseIcon from './BaseIcon.vue'
import BaseInput from './BaseInput.vue'

export default {
  components: {
    BaseButton,
    BaseIcon,
    BaseInput
  }
}

Just to support relatively little markup in a template:

<BaseInput
  v-model="searchText"
  @keydown.enter="search"
/>
<BaseButton @click="search">
  <BaseIcon name="search"/>
</BaseButton>

Fortunately, if you’re using Webpack (or Vue CLI 3+, which uses Webpack internally), you can use require.context to globally register only these very common base components. Here’s an example of the code you might use to globally import base components in your app’s entry file (e.g. src/main.js):

import Vue from 'vue'
import upperFirst from 'lodash/upperFirst'
import camelCase from 'lodash/camelCase'

const requireComponent = require.context(
  // The relative path of the components folder
  './components',
  // Whether or not to look in subfolders
  false,
  // The regular expression used to match base component filenames
  /Base[A-Z]w+.(vue|js)$/
)

requireComponent.keys().forEach(fileName => {
  // Get component config
  const componentConfig = requireComponent(fileName)

  // Get PascalCase name of component
  const componentName = upperFirst(
    camelCase(
      // Gets the file name regardless of folder depth
      fileName
        .split('/')
        .pop()
        .replace(/.w+$/, '')
    )
  )


  // Register component globally
  Vue.component(
    componentName,
    // Look for the component options on `.default`, which will
    // exist if the component was exported with `export default`,
    // otherwise fall back to module's root.
    componentConfig.default || componentConfig
  )
})

Remember that global registration must take place before the root Vue instance is created (with new Vue). Here’s an example of this pattern in a real project context.