Bredon

Bredon is a modern, specification-driven CSS value compiler in JavaScript.
It's parser uses very detailed nodes and provides as much information as possible.
The generated AST (Abstract Syntax Tree) is simple and readable which allows efficient and straight-forward transormation. It automatically outputs formatted CSS values.

Support Us

Support Robin Frischmann's work on Fela and its ecosystem (Bredon) directly via Patreon.

Or support us on Open Collective to fund community work. This also includes Bredon as well.
Thank you to all our backers!

Installation

yarn add bredon

Alternatively use npm i --save bredon.

Why?

I am heavily involved in the whole CSS in JS movement with Fela and Elodin as well as inline-style-prefixer. While writing Elodin, a plugin-based style object linter, I struggled to do complex value validation and value transformation. As CSS values are just plain strings, we do not have any meaningful types.
But, in order to perform efficient validation and transformation, we have to parse CSS values into useful type-aware components. That's where Bredon joins the game. It uses a specification-driven value parser that provides the required degree of accuracy and detail.

Bredon also serves as a personal project to learn and understand how compilers work.

How?

I heavily used James Kyle's the-super-tiny-compiler to build Bredon. It follows the exact same steps as any other compiler does:

1. First of all we read the input, one by one, and generate tokens
2. Then we parse these tokens into syntactic nodes, also know as AST
3. (optional) We may now traverse the AST and transform nodes
4. Finally we generate a new CSS value using the transformed AST

The Gist

import { parse, generate } from 'bredon'

const input = '10px solid rgba(255, 0, 255, 0.55)'
const ast = parse(input)

ast === {
  type: 'ValueList',
  body: [{
    type: 'Value',
    important: false,
    body: [{
      type: 'Dimension',
      unit: 'px',
      value: {
        type: 'Integer',
        negative: false,
        value: 10
      }
    }, {
      type: 'Identifier',
      value: 'solid'
    }, {
      type: 'FunctionExpression',
      callee: 'rgba',
      params: [{
        type: 'Integer',
        negative: false,
        value: 255
      }, {
        type: 'Integer',
        negative: false,
        value: 0
      }, {
        type: 'Integer',
        negative: true,
        value: 255
      }, {
        type: 'Float',
        negative: false,
        fractional: 0.55,
        integer: 0,
      }]
    }]
  }]
}

const output = generate(ast)

console.log(output)
// => 10px solid rgba(255, 0, 255, 0.55)

// parsing and generation can be combined
const output = compile(input)

Documentation

• API Reference
  • bredon
    • parse
    • traverse
    • generate
    • compile
    • types
  • bredon-types
    • Validators
    • Builders
  • bredon-validate
    • validate
  • bredon-minify
    • minify
• AST Nodes
  • Identifier
  • Operator
  • HexColor
  • Parenthesis
  • URL
  • StringLiteral
  • Assignment
  • Dimension
  • Integer
  • Float
  • FunctionExpression
  • Expression

Plugins

Bredon's most powerful part is its extendable plugin system.
Plugins are used to analyze and transform AST nodes.

Plugin	Version	Size	Description
calc			Precalculate calc() expression as much as possible
case			Normalize letter case for all identifiers
color			Manipulate, normalize and minify CSS color values
initial			Replace, normalize and minify initial values
precision			Normalize decimal number precision
remove-unit			Remove unnecessary value units
trim-hex			Minify hex color values if possible
unit			Convert, normalize and minify unit values

Integrations

To use Bredon within your project, you will need to somehow integrate the compiler into your workflow.
Currently, we support to options to do so. You can either use Bredon with your existing CSS codebase using PostCSS. For JavaScript-based styling solutions (CSS in JS), there is Elodin which can be configured to auto-fix styles.

• elodin
• postcss-bredon

PostCSS Stand-Alones

You can also use bredon-minify and bredon-validate as a stand-alone plugin for PostCSS:

• postcss-bredon-minify
• postcss-bredon-validate

Support

Join us on Gitter.
We highly appreciate any contribution.
We also love to get feedback.

License

Bredon is licensed under the MIT License.
Documentation is licensed under Creative Common License.
Created with ♥ by @rofrischmann.