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2019-08-11 18:48:02 +00:00
## @vue/babel-plugin-transform-vue-jsx
> Babel plugin for Vue 2.0 JSX
### Babel Compatibility Notes
- This repo is only compatible with Babel 7.x, for 6.x please use [vuejs/babel-plugin-transform-vue-jsx](https://github.com/vuejs/babel-plugin-transform-vue-jsx)
### Requirements
- Assumes you are using Babel with a module bundler e.g. Webpack, because the spread merge helper is imported as a module to avoid duplication.
- This is mutually exclusive with `babel-plugin-transform-react-jsx`.
### Usage
```bash
npm install @vue/babel-plugin-transform-vue-jsx --save-dev
npm install @vue/babel-helper-vue-jsx-merge-props --save
```
In your `.babelrc`:
```json
{
"plugins": ["transform-vue-jsx"]
}
```
However it is recommended to use the [configurable preset](../babel-preset-jsx/README.md) instead.
### Details
The plugin transpiles the following JSX:
```jsx
<div id="foo">{this.text}</div>
```
To the following JavaScript:
```js
h(
'div',
{
attrs: {
id: 'foo',
},
},
[this.text],
)
```
Note the `h` function, which is a shorthand for a Vue instance's `$createElement` method, must be in the scope where the JSX is. Since this method is passed to component render functions as the first argument, in most cases you'd do this:
```js
Vue.component('jsx-example', {
render(h) {
// <-- h must be in scope
return <div id="foo">bar</div>
},
})
```
### Difference from React JSX
First, Vue 2.0's vnode format is different from React's. The second argument to the `createElement` call is a "data object" that accepts nested objects. Each nested object will be then processed by corresponding modules:
```js
render (h) {
return h('div', {
// Component props
props: {
msg: 'hi'
},
// Normal HTML attributes
attrs: {
id: 'foo'
},
// DOM props
domProps: {
innerHTML: 'bar'
},
// Event handlers are nested under "on", though
// modifiers such as in v-on:keyup.enter are not
// supported. You'll have to manually check the
// keyCode in the handler instead.
on: {
click: this.clickHandler
},
// For components only. Allows you to listen to
// native events, rather than events emitted from
// the component using vm.$emit.
nativeOn: {
click: this.nativeClickHandler
},
// Class is a special module, same API as `v-bind:class`
class: {
foo: true,
bar: false
},
// Style is also same as `v-bind:style`
style: {
color: 'red',
fontSize: '14px'
},
// Other special top-level properties
key: 'key',
ref: 'ref',
// Assign the `ref` is used on elements/components with v-for
refInFor: true,
slot: 'slot'
})
}
```
The equivalent of the above in Vue 2.0 JSX is:
```jsx
render (h) {
return (
<div
// Component props
propsMsg="hi"
// Normal attributes or component props.
id="foo"
// DOM properties are prefixed with `domProps`
domPropsInnerHTML="bar"
// event listeners are prefixed with `on` or `nativeOn`
onClick={this.clickHandler}
nativeOnClick={this.nativeClickHandler}
// other special top-level properties
class={{ foo: true, bar: false }}
style={{ color: 'red', fontSize: '14px' }}
key="key"
ref="ref"
// assign the `ref` is used on elements/components with v-for
refInFor
slot="slot">
</div>
)
}
```
### Component Tip
If a custom element starts with lowercase, it will be treated as a string id and used to lookup a registered component. If it starts with uppercase, it will be treated as an identifier, which allows you to do:
```js
import Todo from './Todo.js'
export default {
render(h) {
return <Todo /> // no need to register Todo via components option
},
}
```
### JSX Spread
JSX spread is supported, and this plugin will intelligently merge nested data properties. For example:
```jsx
const data = {
class: ['b', 'c'],
}
const vnode = <div class="a" {...data} />
```
The merged data will be:
```js
{ class: ['a', 'b', 'c'] }
```
### Vue directives
Vue directives are usable the same way as in template with a few key differences:
1. You can use directives camelCased instead of kebab-cased (vMyDirective is treated as `v-my-directive`)
2. You have to use underscore sign instead of dots for modifiers because of JSXIdentifier limitation.
3. Only runtime directives work (only v-show and custom directives), compile-time directives are out of this project's scope.
A full example would be: `<MyComponent vMyDirective:argument_modifier1_modifier2={someExpression} />`