Component Instance ​

$data ​

The object returned from the data option, made reactive by the component. The component instance proxies access to the properties on its data object.

• Type

  ts

  interface ComponentPublicInstance {
    $data: object
  }

$props ​

An object representing the component's current, resolved props.

• Type

  ts

  interface ComponentPublicInstance {
    $props: object
  }

• Details

  Only props declared via the props option will be included. The component instance proxies access to the properties on its props object.

$el ​

The root DOM node that the component instance is managing.

• Type

  ts

  interface ComponentPublicInstance {
    $el: any
  }

• Details

  $el will be undefined until the component is mounted.

  • For components with a single root element, $el will point to that element.
  • For components with text root, $el will point to the text node.
  • For components with multiple root nodes, $el will be the placeholder DOM node that Vue uses to keep track of the component's position in the DOM (a text node, or a comment node in SSR hydration mode).

  TIP

  For consistency, it is recommended to use template refs for direct access to elements instead of relying on $el.

$options ​

The resolved component options used for instantiating the current component instance.

• Type

  ts

  interface ComponentPublicInstance {
    $options: ComponentOptions
  }

• Details

  The $options object exposes the resolved options for the current component and is the merge result of these possible sources:

  • Global mixins
  • Component extends base
  • Component mixins

  It is typically used to support custom component options:

  js

  const app = createApp({
    customOption: 'foo',
    created() {
      console.log(this.$options.customOption) // => 'foo'
    }
  })

• See also app.config.optionMergeStrategies

$parent ​

The parent instance, if the current instance has one. It will be null for the root instance itself.

• Type

  ts

  interface ComponentPublicInstance {
    $parent: ComponentPublicInstance | null
  }

$root ​

The root component instance of the current component tree. If the current instance has no parents this value will be itself.

• Type

  ts

  interface ComponentPublicInstance {
    $root: ComponentPublicInstance
  }

$slots ​

An object representing the slots passed by the parent component.

• Type

  ts

  interface ComponentPublicInstance {
    $slots: { [name: string]: Slot }
  }
  
  type Slot = (...args: any[]) => VNode[]

• Details

  Typically used when manually authoring render functions, but can also be used to detect whether a slot is present.

  Each slot is exposed on this.$slots as a function that returns an array of vnodes under the key corresponding to that slot's name. The default slot is exposed as this.$slots.default.

  If a slot is a scoped slot, arguments passed to the slot functions are available to the slot as its slot props.

• See also Render Functions - Rendering Slots

$refs ​

An object of DOM elements and component instances, registered via template refs.

• Type

  ts

  interface ComponentPublicInstance {
    $refs: { [name: string]: Element | ComponentPublicInstance | null }
  }

• See also

  • Template refs
  • Special Attributes - ref

$attrs ​

An object that contains the component's fallthrough attributes.

• Type

  ts

  interface ComponentPublicInstance {
    $attrs: object
  }

• Details

  Fallthrough Attributes are attributes and event handlers passed by the parent component, but not declared as a prop or an emitted event by the child.

  By default, everything in $attrs will be automatically inherited on the component's root element if there is only a single root element. This behavior is disabled if the component has multiple root nodes, and can be explicitly disabled with the inheritAttrs option.

• See also

  • Fallthrough Attributes

$watch() ​

Imperative API for creating watchers.

• Type

  ts

  interface ComponentPublicInstance {
    $watch(
      source: string | (() => any),
      callback: WatchCallback,
      options?: WatchOptions
    ): StopHandle
  }
  
  type WatchCallback<T> = (
    value: T,
    oldValue: T,
    onCleanup: (cleanupFn: () => void) => void
  ) => void
  
  interface WatchOptions {
    immediate?: boolean // default: false
    deep?: boolean // default: false
    flush?: 'pre' | 'post' | 'sync' // default: 'pre'
    onTrack?: (event: DebuggerEvent) => void
    onTrigger?: (event: DebuggerEvent) => void
  }
  
  type StopHandle = () => void

• Details

  The first argument is the watch source. It can be a component property name string, a simple dot-delimited path string, or a getter function.

  The second argument is the callback function. The callback receives the new value and the old value of the watched source.

  • immediate: trigger the callback immediately on watcher creation. Old value will be undefined on the first call.
  • deep: force deep traversal of the source if it is an object, so that the callback fires on deep mutations. See Deep Watchers.
  • flush: adjust the callback's flush timing. See Callback Flush Timing and watchEffect().
  • onTrack / onTrigger: debug the watcher's dependencies. See Watcher Debugging.

• Example

  Watch a property name:

  js

  this.$watch('a', (newVal, oldVal) => {})

  Watch a dot-delimited path:

  js

  this.$watch('a.b', (newVal, oldVal) => {})

  Using getter for more complex expressions:

  js

  this.$watch(
    // every time the expression `this.a + this.b` yields
    // a different result, the handler will be called.
    // It's as if we were watching a computed property
    // without defining the computed property itself.
    () => this.a + this.b,
    (newVal, oldVal) => {}
  )

  Stopping the watcher:

  js

  const unwatch = this.$watch('a', cb)
  
  // later...
  unwatch()

• See also

  • Options - watch
  • Guide - Watchers

$emit() ​

Trigger a custom event on the current instance. Any additional arguments will be passed into the listener's callback function.

• Type

  ts

  interface ComponentPublicInstance {
    $emit(event: string, ...args: any[]): void
  }

• Example

  js

  export default {
    created() {
      // only event
      this.$emit('foo')
      // with additional arguments
      this.$emit('bar', 1, 2, 3)
    }
  }

• See also

  • Component - Events
  • emits option

$forceUpdate() ​

Force the component instance to re-render.

• Type

  ts

  interface ComponentPublicInstance {
    $forceUpdate(): void
  }

• Details

  This should be rarely needed given Vue's fully automatic reactivity system. The only cases where you may need it is when you have explicitly created non-reactive component state using advanced reactivity APIs.

$nextTick() ​

Instance-bound version of the global nextTick().

• Type

  ts

  interface ComponentPublicInstance {
    $nextTick(callback?: (this: ComponentPublicInstance) => void): Promise<void>
  }

• Details

  The only difference from the global version of nextTick() is that the callback passed to this.$nextTick() will have its this context bound to the current component instance.

• See also nextTick()