fela-identifier

fela-identifier

This enhancer allows you to create rules for which the renderer will generate unique class names.

Installation

yarn add fela-identifier

You may alternatively use npm i --save fela-identifier.

Problem

Sometimes it is necessary to additionally stylize (for example, highlight) some DOM element when manipulating (for example, when hovering) with the parent. In classical CSS this would look something like this:

.parent-element:hover .child-element {
  background-color: red; 
}

But with Fela, this is not so easy, because you do not assign classes yourself.

Solution

Create a rule for which the renderer will predictably generate the same unique class name.

Usage

import { createRenderer } from 'fela'
import createIdentifier from 'fela-identifier'

const identifier = createIdentifier()
const renderer = createRenderer({
  enhancers: [ identifier ]
})

const childElementRule = identifier()
const parentElementRule = () => ({
  [`:hover .${childElementRule}`]: {
    backgroundColor: 'red',
  }
})

renderer.renderRule(childElementRule)
// => 'fela-identifier-0'
renderer.renderRule(parentElementRule)
// => 'a'

outputs

.a:hover .fela-identifier-0 {
  background-color: red
}

API

The module exports a function that creates an identifier. The identifier is both an enhancer and a factory of unique rules. As a factory of unique rules, the identifier has the following API:

Arguments

1. name (String): This is a string that can be used to produce an identifier. Sometimes this is convenient for debugging or visibility.

Returns

(Function): A Fela rule that can be rendered. It also has a field className and an overridden method toString that returns the same value as the field className. You can use it like this:

import createIdentifier from 'fela-identifier'

const identifier = createIdentifier()

const rule = identifier()
const className = rule.className
rule.toString()

!!!Attention!!! Do not use the identifier as a factory before you connect it as an enhancer. This will result in a runtime error.

Configuration

Options

Option	Value	Default	Description
prefix	(string)	fela-identifier	a prefix to be inserted at the beginning of the identifying class
generator	(name: string, index: number) => string	just returns the index	function that is responsible for generating identifiers based on the name and index

Example

import { createRenderer } from 'fela'
import createIdentifier from 'fela-identifier'
import uuidv4 from 'uuid/v4'
import hash from 'object-hash'

const identifier = createIdentifier({
  prefix: 'my-custom-prefix',
  generator: (name, index) => `${hash([name, index])}-${uuidv4()}`,
})

const renderer = createRenderer({
  enhancers: [ identifier ]
})

Examples

Usage with react-fela:

import * as React from 'react'
import * as ReactDOM from 'react-dom'
import { Provider, connect } from 'react-fela'
import { createRenderer } from 'fela'
import createIdentifier from 'fela-identifier'

export const identifier = createIdentifier()
export const renderer = createRenderer({
  enhancers: [ identifier ],
})

let Component = ({ styles }) => (
    <div className={styles.parent}>
      Some Parent Content
      <div className={styles.child}>
        Some Child Content
      </div>
    </div>
)

const child = identifier()
Component = connect({
  parent: {
    [`:hover .${child}`]: {
      backgroundColor: 'red',
    }
  },
  child
})(Component)

ReactDOM.render(
  <Provider renderer={renderer}>
    <Component />
  </Provider>,
  document.getElementById("root"),
)

You can combine identifying rules with styles and with each other:

import { createRenderer, combineRules } from 'fela'
import createIdentifier from 'fela-identifier'

export const identifier = createIdentifier()
export const renderer = createRenderer({
  enhancers: [ identifier ],
})

const firstId = identifier('first')
const secondId = identifier('second')
const someStyle = () => ({
  fontSize: '20px',
  backgroundColor: 'red',
})

const combinedRule = combineRules(
  firstId,
  secondId,
  someStyle,
)

renderer.renderRule(combinedRule)
// => 'a b fela-identifier-first-0 fela-identifier-second-1'

License

Fela is licensed under the MIT License.
Documentation is licensed under Creative Common License.
Created with ♥ by @rofrischmann and all the great contributors.