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

The set of tools for working with CSS, including fast detailed parser (string->AST), walkers, generators (AST->string) and even lexer (validation and matching) based on knowledge of spec and browser implementations (see schema for details). The main goal to be efficient and W3C spec complient, with focus on analyzing and source-to-source processing.

Work in progress. The project in alpha stage since some parts need further experiments, AST format and API are subjects to change. However it's stable enough and used by packages like CSSO (CSS minifier) in production.

• Parsing CSS into AST
• AST format
• Translate AST to string
• AST traversal
• Utils to work with AST

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 === 'ClassSelector' && node.name === 'example') {
        node.name = 'hello';
    }
});

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

Top level API

License

MIT

Syntax matching uses mdn/data by Mozilla Contributors

Changelog

1.0.0-alpha25 (October 9, 2017)

• Parser
  • Added fallback node as argument to onParseError() handler
  • Fixed raw consuming in tolerant mode when selector is invalid (greedy consuming and redundant warnings)
  • Fixed exception in tolerant mode caused by unknown at-rule with unclosed block
  • Changed handling of semicolons:
    • Hanging semicolon inside declaration blocks raise an error or turns into a Raw node in tolerant mode instead of being ignored
    • Semicolon outside of declaration blocks opens a Rule node as part of selector instead of being ignored
  • Aligned parseAtrulePrelude behaviour to parseRulePrelude
    • Removed Raw node wraping into AtrulePrelude when parseAtrulePrelude is disabled
    • Removed error emitting when at-rule has a custom prelude customer but no prelude is found (it should be validated by a lexer later)
• Generator
  • Fixed performance issue with translateWithSourceMap(), flattening the string (because of mixing building string and indexing into it) turned it into a quadratic algorithm (approximate numbers can be found in the quiz created by this case)
• Added support for a single solidus hack for property()
• Minor fixes for custom errors