# Global API

If you're using a CDN build then the functions of the global API are accessible via the global Vue object. e.g.:

const { createApp, h, nextTick } = Vue

If you're using ES modules then they can be imported directly:

import { createApp, h, nextTick } from 'vue'

Global functions that handle reactivity, such as reactive and ref, are documented separately. See Reactivity API for those functions.

# createApp

Returns an application instance which provides an application context. The entire component tree mounted by the application instance share the same context.

const app = createApp({})

You can chain other methods after createApp, they can be found in Application API

# Arguments

The function receives a root component options object as a first parameter:

const app = createApp({
  data() {
    return {
      ...
    }
  },
  methods: {...},
  computed: {...}
  ...
})

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With the second parameter, we can pass root props to the application:

const app = createApp(
  {
    props: ['username']
  },
  { username: 'Evan' }
)

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<div id="app">
  <!-- Will display 'Evan' -->
  {{ username }}
</div>

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The root props are raw props, much like those passed to h to create a VNode. In addition to component props, they can also include attributes and event listeners to be applied to the root component.

# Typing

interface Data {
  [key: string]: unknown
}

export type CreateAppFunction<HostElement> = (
  rootComponent: PublicAPIComponent,
  rootProps?: Data | null
) => App<HostElement>

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# h

Returns a "virtual node", usually abbreviated to VNode: a plain object which contains information describing to Vue what kind of node it should render on the page, including descriptions of any child nodes. It is intended for manually written render functions:

render() {
  return h('h1', {}, 'Some title')
}

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# Arguments

Accepts three arguments: type, props and children

# type

Type: String | Object | Function
Details:

An HTML tag name, a component, an async component, or a functional component. Using function returning null would render a comment. This parameter is required

# props

Type: Object
Details:

An object corresponding to the attributes, props and events we would use in a template. Optional

# children

Type: String | Array | Object

Details:

Children VNodes, built using h(), or using strings to get "text VNodes" or an object with slots. Optional

h('div', {}, [
  'Some text comes first.',
  h('h1', 'A headline'),
  h(MyComponent, {
    someProp: 'foobar'
  })
])

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# defineComponent

Implementation-wise defineComponent does nothing but return the object passed to it. However, in terms of typing, the returned value has a synthetic type of a constructor for manual render function, TSX and IDE tooling support.

# Arguments

An object with component options

import { defineComponent } from 'vue'

const MyComponent = defineComponent({
  data() {
    return { count: 1 }
  },
  methods: {
    increment() {
      this.count++
    }
  }
})

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Or a setup function, function name will be used as component name

import { defineComponent, ref } from 'vue'

const HelloWorld = defineComponent(function HelloWorld() {
  const count = ref(0)
  return { count }
})

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# defineAsyncComponent

Creates an async component that will be loaded only when it's necessary.

# Arguments

For basic usage, defineAsyncComponent can accept a factory function returning a Promise. Promise's resolve callback should be called when you have retrieved your component definition from the server. You can also call reject(reason) to indicate the load has failed.

import { defineAsyncComponent } from 'vue'

const AsyncComp = defineAsyncComponent(() =>
  import('./components/AsyncComponent.vue')
)

app.component('async-component', AsyncComp)

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When using local registration, you can also directly provide a function that returns a Promise:

import { createApp, defineAsyncComponent } from 'vue'

createApp({
  // ...
  components: {
    AsyncComponent: defineAsyncComponent(() =>
      import('./components/AsyncComponent.vue')
    )
  }
})

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For advanced usage, defineAsyncComponent can accept an object of the following format:

import { defineAsyncComponent } from 'vue'

const AsyncComp = defineAsyncComponent({
  // The factory function
  loader: () => import('./Foo.vue'),
  // A component to use while the async component is loading
  loadingComponent: LoadingComponent,
  // A component to use if the load fails
  errorComponent: ErrorComponent,
  // Delay before showing the loading component. Default: 200ms.
  delay: 200,
  // The error component will be displayed if a timeout is
  // provided and exceeded. Default: Infinity.
  timeout: 3000,
  // Defining if component is suspensible. Default: true.
  suspensible: false,
  /**
   *
   * @param {*} error Error message object
   * @param {*} retry A function that indicating whether the async component should retry when the loader promise rejects
   * @param {*} fail  End of failure
   * @param {*} attempts Maximum allowed retries number
   */
  onError(error, retry, fail, attempts) {
    if (error.message.match(/fetch/) && attempts <= 3) {
      // retry on fetch errors, 3 max attempts
      retry()
    } else {
      // Note that retry/fail are like resolve/reject of a promise:
      // one of them must be called for the error handling to continue.
      fail()
    }
  },
})

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See also: Dynamic and Async components

# defineCustomElement 3.2+

This method accepts the same argument as defineComponent, but instead returns a native Custom Element (opens new window) that can be used within any framework, or with no frameworks at all.

Usage example:

<my-vue-element></my-vue-element>

import { defineCustomElement } from 'vue'

const MyVueElement = defineCustomElement({
  // normal Vue component options here
  props: {},
  emits: {},
  template: `...`,

  // defineCustomElement only: CSS to be injected into shadow root
  styles: [`/* inlined css */`]
})

// Register the custom element.
// After registration, all `<my-vue-element>` tags on the page will be upgraded.
customElements.define('my-vue-element', MyVueElement)

// You can also programmatically instantiate the element:
// (can only be done after registration)
document.body.appendChild(
  new MyVueElement({
    // initial props (optional)
  })
)

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For more details on building Web Components with Vue, especially with Single File Components, see Vue and Web Components.

# resolveComponent

WARNING

resolveComponent can only be used within render or setup functions.

Allows resolving a component by its name, if it is available in the current application instance.

Returns a Component or the argument name when not found.

const app = createApp({})
app.component('MyComponent', {
  /* ... */
})

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import { resolveComponent } from 'vue'
render() {
  const MyComponent = resolveComponent('MyComponent')
}

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# Arguments

Accepts one argument: name

# name

Type: String
Details:

The name of a loaded component.

# resolveDynamicComponent

WARNING

resolveDynamicComponent can only be used within render or setup functions.

Allows resolving a component by the same mechanism that <component :is=""> employs.

Returns the resolved Component or a newly created VNode with the component name as the node tag. Will raise a warning if the Component was not found.

import { resolveDynamicComponent } from 'vue'
render () {
  const MyComponent = resolveDynamicComponent('MyComponent')
}

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# Arguments

Accepts one argument: component

# component

Type: String | Object (component’s options object)
Details:

For more details, refer to the documentation on Dynamic Components.

# resolveDirective

WARNING

resolveDirective can only be used within render or setup functions.

Allows resolving a directive by its name, if it is available in the current application instance.

Returns a Directive or undefined when not found.

const app = createApp({})
app.directive('highlight', {})

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import { resolveDirective } from 'vue'
render () {
  const highlightDirective = resolveDirective('highlight')
}

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# Arguments

Accepts one argument: name

# name

Type: String
Details:

The name of a loaded directive.

# withDirectives

WARNING

withDirectives can only be used within render or setup functions.

Allows applying directives to a VNode. Returns a VNode with the applied directives.

import { withDirectives, resolveDirective } from 'vue'
const foo = resolveDirective('foo')
const bar = resolveDirective('bar')

return withDirectives(h('div'), [
  [foo, this.x],
  [bar, this.y]
])

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# Arguments

Accepts two arguments: vnode and directives.

# vnode

Type: vnode
Details:

A virtual node, usually created with h().

# directives

Type: Array

Details:

An array of directives.

Each directive itself is an array, which allows for up to 4 indexes to be defined as seen in the following examples.

[directive] - The directive by itself. Required.

const MyDirective = resolveDirective('MyDirective')
const nodeWithDirectives = withDirectives(h('div'), [[MyDirective]])

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[directive, value] - The above, plus a value of type any to be assigned to the directive

const MyDirective = resolveDirective('MyDirective')
const nodeWithDirectives = withDirectives(h('div'), [[MyDirective, 100]])

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[directive, value, arg] - The above, plus a String argument, ie. click in v-on:click

const MyDirective = resolveDirective('MyDirective')
const nodeWithDirectives = withDirectives(h('div'), [
  [MyDirective, 100, 'click']
])

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[directive, value, arg, modifiers] - The above, plus a key: value pair Object defining any modifiers.

const MyDirective = resolveDirective('MyDirective')
const nodeWithDirectives = withDirectives(h('div'), [
  [MyDirective, 100, 'click', { prevent: true }]
])

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# createRenderer

The createRenderer function accepts two generic arguments: HostNode and HostElement, corresponding to Node and Element types in the host environment.

For example, for runtime-dom, HostNode would be the DOM Node interface and HostElement would be the DOM Element interface.

Custom renderers can pass in the platform specific types like this:

import { createRenderer } from 'vue'
const { render, createApp } = createRenderer<Node, Element>({
  patchProp,
  ...nodeOps
})

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# Arguments

Accepts two arguments: HostNode and HostElement

# HostNode

Type: Node
Details:

The node in the host environment.

# HostElement

Type: Element
Details:

The element in the host environment.

# nextTick

Defer the callback to be executed after the next DOM update cycle. Use it immediately after you’ve changed some data to wait for the DOM update.

import { createApp, nextTick } from 'vue'

const app = createApp({
  setup() {
    const message = ref('Hello!')
    const changeMessage = async newMessage => {
      message.value = newMessage
      await nextTick()
      console.log('Now DOM is updated')
    }
  }
})

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See also: $nextTick instance method

# mergeProps

Takes multiple objects containing VNode props and merges them into a single object. A newly created object is returned, the objects passed as arguments are not modified.

Any number of objects can be passed, with properties from later arguments taking precedence. Event listeners are handled specially, as are class and style, with the values of these properties being merged rather than overwritten.

import { h, mergeProps } from 'vue'

export default {
  inheritAttrs: false,

  render() {
    const props = mergeProps(
      {
        // The class will be merged with any class from $attrs
        class: 'active'
      },
      this.$attrs
    )

    return h('div', props)
  }
}

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# useCssModule

WARNING

useCssModule can only be used within render or setup functions.

Allows CSS modules to be accessed within the setup function of a single-file component:

<script>
import { h, useCssModule } from 'vue'

export default {
  setup() {
    const style = useCssModule()

    return () =>
      h(
        'div',
        {
          class: style.success
        },
        'Task complete!'
      )
  }
}
</script>

<style module>
.success {
  color: #090;
}
</style>

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For more information about using CSS modules, see SFC Style Features: <style module>.

# Arguments

Accepts one argument: name

# name

Type: String
Details:

The name of the CSS module. Defaults to '$style'.

# version

Provides the installed version of Vue as a string.

const version = Number(Vue.version.split('.')[0])

if (version === 3) {
  // Vue 3
} else if (version === 2) {
  // Vue 2
} else {
  // Unsupported versions of Vue
}

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See also: Application API - version