babel-plugin-transform-vue-jsx

babel-plugin-transform-vue-jsx

Babel plugin for Vue 2.0 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

npm install\
  babel-plugin-syntax-jsx\
  babel-plugin-transform-vue-jsx\
  babel-helper-vue-jsx-merge-props\
  --save-dev

In your .babelrc:

{
  "presets": ["es2015"],
  "plugins": ["transform-vue-jsx"]
}

The plugin transpiles the following JSX:

<div id="foo">{this.text}</div>

To the following JavaScript:

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:

Vue.component('jsx-example', {
  render (h) { // <-- h must be in scope
    return <div id="foo">bar</div>
  }
})

h auto-injection

Starting with version 3.4.0 we automatically inject const h = this.$createElement in any method and getter declared in ES2015 syntax that has JSX so you can drop the (h) parameter.

Vue.component('jsx-example', {
  render () { // h will be injected
    return <div id="foo">bar</div>
  },
  myMethod: function () { // h will not be injected
    return <div id="foo">bar</div>
  }
})

Important h does not inject into functions or arrow functions, it works only in ES2015 Method Properties declaration.

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:

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:

render (h) {
  return (
    <div
      // 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:

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:

const data = {
  class: ['b', 'c']
}
const vnode = <div class="a" {...data}/>

The merged data will be:

{ class: ['a', 'b', 'c'] }

Vue directives

Note that almost all built-in Vue directives are not supported when using JSX, the sole exception being v-show, which can be used with the v-show={value} syntax. In most cases there are obvious programmatic equivalents, for example v-if is just a ternary expression, and v-for is just an array.map() expression, etc.

For custom directives, you can use the v-name={value} syntax. However, note that directive arguments and modifiers are not supported using this syntax. There are two workarounds:

1. Pass everything as an object via value, e.g. v-name={{ value, modifier: true }}

2. Use the raw vnode directive data format:

const directives = [
  { name: 'my-dir', value: 123, modifiers: { abc: true } }
]

return <div {...{ directives }}/>