Render Function APIs
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Render Function APIs#
h()#
Creates virtual DOM nodes (vnodes).
- Type
```ts // full signature function h( type: string | Component, props?: object | null, children?: Children | Slot | Slots ): VNode
// omitting props function h(type: string | Component, children?: Children | Slot): VNode
type Children = string | number | boolean | VNode | null | Children[]
type Slot = () => Children
type Slots = { [name: string]: Slot } ```
Types are simplified for readability.
- Details
The first argument can either be a string (for native elements) or a Vue component definition. The second argument is the props to be passed, and the third argument is the children.
When creating a component vnode, the children must be passed as slot functions. A single slot function can be passed if the component expects only the default slot. Otherwise, the slots must be passed as an object of slot functions.
For convenience, the props argument can be omitted when the children is not a slots object.
- Example
Creating native elements:
```js import { h } from 'vue'
// all arguments except the type are optional h('div') h('div', { id: 'foo' })
// both attributes and properties can be used in props // Vue automatically picks the right way to assign it h('div', { class: 'bar', innerHTML: 'hello' })
// class and style have the same object / array // value support like in templates h('div', { class: [foo, { bar }], style: { color: 'red' } })
// event listeners should be passed as onXxx h('div', { onClick: () => {} })
// children can be a string h('div', { id: 'foo' }, 'hello')
// props can be omitted when there are no props h('div', 'hello') h('div', [h('span', 'hello')])
// children array can contain mixed vnodes and strings h('div', ['hello', h('span', 'hello')]) ```
Creating components:
```js import Foo from './Foo.vue'
// passing props h(Foo, { // equivalent of some-prop="hello" someProp: 'hello', // equivalent of @update="() => {}" onUpdate: () => {} })
// passing single default slot h(Foo, () => 'default slot')
// passing named slots
// notice the null is required to avoid
// slots object being treated as props
h(MyComponent, null, {
default: () => 'default slot',
foo: () => h('div', 'foo'),
bar: () => [h('span', 'one'), h('span', 'two')]
})
```
mergeProps()#
Merge multiple props objects with special handling for certain props.
- Type
ts
function mergeProps(...args: object[]): object
- Details
mergeProps() supports merging multiple props objects with special handling for the following props:
classstyleonXxxevent listeners - multiple listeners with the same name will be merged into an array.
If you do not need the merge behavior and want simple overwrites, native object spread can be used instead.
- Example
```js import { mergeProps } from 'vue'
const one = { class: 'foo', onClick: handlerA }
const two = { class: { bar: true }, onClick: handlerB }
const merged = mergeProps(one, two) /* { class: 'foo bar', onClick: [handlerA, handlerB] } / ```
cloneVNode()#
Clones a vnode.
- Type
ts
function cloneVNode(vnode: VNode, extraProps?: object): VNode
- Details
Returns a cloned vnode, optionally with extra props to merge with the original.
Vnodes should be considered immutable once created, and you should not mutate the props of an existing vnode. Instead, clone it with different / extra props.
Vnodes have special internal properties, so cloning them is not as simple as an object spread. cloneVNode() handles most of the internal logic.
- Example
```js import { h, cloneVNode } from 'vue'
const original = h('div') const cloned = cloneVNode(original, { id: 'foo' }) ```
isVNode()#
Checks if a value is a vnode.
- Type
ts
function isVNode(value: unknown): boolean
resolveComponent()#
For manually resolving a registered component by name.
- Type
ts
function resolveComponent(name: string): Component | string
- Details
Note: you do not need this if you can import the component directly.
resolveComponent() must be called inside either setup() or the render function in order to resolve from the correct component context.
If the component is not found, a runtime warning will be emitted, and the name string is returned.
- Example
resolveDirective()#
For manually resolving a registered directive by name.
- Type
ts
function resolveDirective(name: string): Directive | undefined
- Details
Note: you do not need this if you can import the directive directly.
resolveDirective() must be called inside either setup() or the render function in order to resolve from the correct component context.
If the directive is not found, a runtime warning will be emitted, and the function returns undefined.
withDirectives()#
For adding custom directives to vnodes.
- Type
```ts function withDirectives( vnode: VNode, directives: DirectiveArguments ): VNode
// [Directive, value, argument, modifiers] type DirectiveArguments = Array< | [Directive] | [Directive, any] | [Directive, any, string] | [Directive, any, string, DirectiveModifiers]
```
- Details
Wraps an existing vnode with custom directives. The second argument is an array of custom directives. Each custom directive is also represented as an array in the form of [Directive, value, argument, modifiers]. Tailing elements of the array can be omitted if not needed.
- Example
```js import { h, withDirectives } from 'vue'
// a custom directive const pin = { mounted() { / ... / }, updated() { / ... / } }
//
const vnode = withDirectives(h('div'), [ [pin, 200, 'top', { animate: true }] ]) ```withModifiers()#
For adding built-in v-on modifiers to an event handler function.
- Type
ts
function withModifiers(fn: Function, modifiers: ModifierGuardsKeys[]): Function
- Example
```js import { h, withModifiers } from 'vue'
const vnode = h('button', { // equivalent of v-on:click.stop.prevent onClick: withModifiers(() => { // ... }, ['stop', 'prevent']) }) ```