css-tree

What is css-tree?

The css-tree npm package is a tool for parsing and manipulating CSS. It allows users to parse CSS strings into an abstract syntax tree (AST), walk over nodes in the tree, generate CSS strings, and more. It is useful for tasks such as CSS minification, linting, and transformation.

What are css-tree's main functionalities?

Parsing CSS to AST

This feature allows you to parse a CSS string and convert it into an abstract syntax tree (AST) for further manipulation or analysis.

const csstree = require('css-tree');
const ast = csstree.parse('.example { color: red; }');

Walking the AST

This feature enables you to traverse the AST and apply functions or extract information from specific nodes.

csstree.walk(ast, function(node) {
  if (node.type === 'ClassSelector') {
    console.log(node.name);
  }
});

Generating CSS from AST

After manipulating the AST, you can generate a CSS string from the modified AST, which can be used in stylesheets or injected into web pages.

const modifiedAST = csstree.parse('.example { color: blue; }');
const css = csstree.generate(modifiedAST);

Minifying CSS

css-tree can be used to minify CSS by parsing it with compression options and then translating the AST back to a CSS string.

const compressedCSS = csstree.translate(csstree.parse('.example { color: red; }', { compress: true }));

Other packages similar to css-tree

postcss

PostCSS is a tool for transforming CSS with JavaScript plugins. It can do similar tasks as css-tree, such as parsing, walking the AST, and generating CSS. PostCSS is plugin-based, which makes it more extensible and allows for a wide range of transformations.

sass

Sass is a preprocessor scripting language that is interpreted or compiled into CSS. It offers more syntactic features compared to css-tree, such as variables, nesting, and mixins, but it is not primarily focused on parsing and manipulating existing CSS.

less

Less is another CSS pre-processor, similar to Sass, that extends the capabilities of CSS with dynamic behavior such as variables, mixins, operations, and functions. Less and css-tree serve different purposes, with Less focusing on writing CSS in a more functional way and css-tree on parsing and manipulation.

clean-css

clean-css is a fast and efficient CSS optimizer for Node.js and the browser. It focuses on minification, which is one of the features of css-tree, but does not provide a general-purpose CSS parsing and manipulation API.

README

CSSTree

Fast detailed CSS parser

Work in progress. Project in alpha stage since AST format is subject to change.

• Parsing CSS into AST
• AST format
• Translate AST to string
• AST traversal
• Utils to work with AST
• Working with syntax
• API references:
  • Tokenizer
  • Parser
  • Lexer
  • List

Docs and tools:

• AST Explorer – explore CSSTree AST format with zero setup
• CSS syntax reference
• CSS syntax validator

Related projects:

• csstree-validator – NPM package to validate CSS
• stylelint-csstree-validator – plugin for stylelint to validate CSS
• Grunt plugin
• Gulp plugin
• Sublime plugin
• VS Code plugin
• Atom plugin

Install

> npm install css-tree

Usage

var csstree = require('css-tree');
var ast = csstree.parse('.example { world: "!" }');

csstree.walk(ast, function(node) {
    if (node.type === 'Class' && node.name === 'example') {
        node.name = 'hello';
    }
});

console.log(csstree.translate(ast));
// .hello{world:"!"}

License

MIT

Syntax matching use mdn/data by Mozilla Contributors

Changelog

1.0.0-alpha15 (February 8, 2017)

• Fixed broken atruleExpression context
• Fixed vendor prefix detection in keyword() and property()
• Fixed property() to not lowercase custom property names
• Added variable boolean flag in property() result
• Renamed scanner into tokenizer
• Ranamed syntax into lexer
• Moved docs/*.html files to csstree/docs repo
• Added element() function for Value context (-moz-element() supported as well)
• Merged Universal node type into Type
• Renamed node types:
  • Id -> IdSelector
  • Class -> ClassSelector
  • Type -> TypeSelector
  • Attribute -> AttributeSelector
  • PseudoClass -> PseudoClassSelector
  • PseudoElement -> PseudoElementSelector
  • Hash -> HexColor
  • Space -> WhiteSpace
  • An+B -> AnPlusB
• Removed Progid node type
• Relaxed MediaQuery consumer to not validate syntax on parse and to include whitespaces in children sequence as is
• Added WhiteSpace.value property to store whitespace sequence
• Implemented parser options to specify what should be parsed in details (when option is false some part of CSS represents as balanced Raw):
  • parseAtruleExpression – to parse at-rule expressions (true by default)
  • parseSelector – to parse rule's selector (true by default)
  • parseValue - to parse declaration's value (true by default)
  • parseCustomProperty – to parse value and fallback of custom property (false by default)
• Changed tokenization to stick leading hyphen minus to identifier token
• Changed selector parsing:
  • Don't convert spaces into descendant combinator
  • Don't validate selector structure on parsing (selectors may be checked by lexer later)
• Initial refactoring of docs
• Various improvements and fixes