Custom JSX pragma

JSX is an XML-like syntax extension to JavaScript.

It's a syntax sugar usually used for React's createElement function.

// example JSX
<div>
  <Button onClick={handleClick}>Hello</Button>
</div>

React.createElement(
  'div',
  null,
  React.createElement(
    Button,
    {
      onClick: handleClick,
    },
    'Hello'
  )
)

Most apps use Babel to compile JSX syntax for use with React or other similar libraries.
By default the Babel plugin will convert JSX into React.createElement.
Libraries like Preact, MDX, Emotion, and Vuejs use custom create elements functions with JSX.

How to change the underlying create element function?

add an option to the Babel plugin — will transform all JSX in an application
set a pragma comment at the beginning of a module — limits the change to only the modules that it's added to

/** @jsx jsx */

import { jsx } from 'my-custom-jsx'

Demo 🚀

/** convert a style object to a CSS class name */
const className = style({color: 'red'});

CSS-in-Js

<span attrs={{ class: style({ color: "blue" }) }} />


// or 


<span className={{ "class-1": true, "class-2": true }} />

<p
  css={{
    margin: 0,
    fontSize: 12,
    color: 'black'
  }}
/>

Emotion,

styled-components,

etc