unique-classname.macro

This is a babel-macros to generate unique className for css-in-js.

If you are coming from CSS modules and want to convert a large code base to emotion, sometimes you might have some empty classNames added to the container div as state of the component.

For example. You might have React component like this

import classNames from 'classnames'
import styles from './styles.css'

const MyComponent = ({ isDisabled }) => (
  <div
    className={classNames(
      styles.container,
      isDisabled ? styles.isDisabled : false
    )}
  >
    <div className={styles.content}>Content</div>
  </div>
)

and your styles looks like this:

.container {
  background: white;
}

.content {
  padding: 10px;

  .disabled & {
    cursor: not-allowed;
    color: '#777';
  }
}

With unique-classname.macro, it will help you generate a hash from both filename and variable name.

Usage

With babel-macros and this package installed, you can use it like this.

import className from 'unique-classname.macro'
import { css } from 'emotion'

const disabledClass = className() // or const disabled = className('disabled')

const containerClass = css`
  background: white;
`

const contentClass = css`
  padding: 10px;

  .${disabled} & {
    cursor: not-allowed;
    color: '#777';
  }
`

const MyComponent = ({ isDisabled }) => (
  <div
    className={classNames(containerClass, isDisabled ? disabledClass : false)}
  >
    <div className={contentClass}>Content</div>
  </div>
)

The above snippet will be compiled in build time:

import className from 'unique-classname.macro'
import { css } from 'emotion'

const disabled = 'disabled-1u6x1nq'

const container = css`
  background: white;
`

const content = css`
  padding: 10px;

  .${disabled} & {
    cursor: not-allowed;
    color: '#777';
  }
`