CSSTree is a tool set for CSS: fast detailed parser (CSS → AST), walker (AST traversal), generator (AST → CSS) and lexer (validation and matching) based on specs and browser implementations. The main goal is to be efficient and W3C spec compliant, with focus on CSS analyzing and source-to-source transforming tasks.
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Detailed parsing with an adjustable level of detail
By default CSSTree parses CSS as detailed as possible, i.e. each single logical part is representing with its own AST node (see AST format for all possible node types). The parsing detail level can be changed through parser options, for example, you can disable parsing of selectors or declaration values for component parts.
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Tolerant to errors by design
Parser behaves as spec says: "When errors occur in CSS, the parser attempts to recover gracefully, throwing away only the minimum amount of content before returning to parsing as normal". The only thing the parser departs from the specification is that it doesn't throw away bad content, but wraps it in a special node type (
Raw) that allows processing it later. -
Fast and efficient
CSSTree is created with focus on performance and effective memory consumption. Therefore it's one of the fastest CSS parsers at the moment.
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Syntax validation
The built-in lexer can test CSS against syntaxes defined by W3C. CSSTree uses mdn/data as a basis for lexer's dictionaries and extends it with vendor specific and legacy syntaxes. Lexer can only check the declaration values and at-rules currently, but this feature will be extended to other parts of the CSS in the future.
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- and more...
- AST format
- Parsing CSS → AST
- Serialization AST → CSS
- AST traversal
- Util functions
- Value encoding & decoding
- List class
- AST transforming
- Value Definition Syntax
- AST Explorer – explore CSSTree AST format with zero setup
- CSS syntax reference
- CSS syntax validator
- 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 with npm:
npm install @eslint/css-tree
Basic usage:
import * as csstree from '@eslint/css-tree';
// parse CSS to AST
const ast = csstree.parse('.example { world: "!" }');
// traverse AST and modify it
csstree.walk(ast, (node) => {
if (node.type === 'ClassSelector' && node.name === 'example') {
node.name = 'hello';
}
});
// generate CSS from AST
console.log(csstree.generate(ast));
// .hello{world:"!"}Syntax matching:
// parse CSS to AST as a declaration value
const ast = csstree.parse('red 1px solid', { context: 'value' });
// match to syntax of `border` property
const matchResult = csstree.lexer.matchProperty('border', ast);
// check first value node is a <color>
console.log(matchResult.isType(ast.children.first, 'color'));
// true
// get a type list matched to a node
console.log(matchResult.getTrace(ast.children.first));
// [ { type: 'Property', name: 'border' },
// { type: 'Type', name: 'color' },
// { type: 'Type', name: 'named-color' },
// { type: 'Keyword', name: 'red' } ]Is it possible to import just a needed part of library like a parser or a walker. That's might useful for loading time or bundle size optimisations.
import * as tokenizer from '@eslint/css-tree/tokenizer';
import * as parser from '@eslint/css-tree/parser';
import * as walker from '@eslint/css-tree/walker';
import * as lexer from '@eslint/css-tree/lexer';
import * as definitionSyntax from '@eslint/css-tree/definition-syntax';
import * as data from '@eslint/css-tree/definition-syntax-data';
import * as dataPatch from '@eslint/css-tree/definition-syntax-data-patch';
import * as utils from '@eslint/css-tree/utils';Bundles are available for use in a browser:
dist/csstree.js– minified IIFE withcsstreeas global
<script src="node_modules/@eslint/css-tree/dist/csstree.js"></script>
<script>
csstree.parse('.example { color: green }');
</script>dist/csstree.esm.js– minified ES module
<script type="module">
import { parse } from 'node_modules/@eslint/css-tree/dist/csstree.esm.js'
parse('.example { color: green }');
</script>One of CDN services like unpkg or jsDelivr can be used. By default (for short path) a ESM version is exposing. For IIFE version a full path to a bundle should be specified:
<!-- ESM -->
<script type="module">
import * as csstree from 'https://cdn.jsdelivr.net/npm/@eslint/css-tree';
import * as csstree from 'https://unpkg.com/@eslint/css-tree';
</script>
<!-- IIFE with an export to global -->
<script src="https://cdn.jsdelivr.net/npm/@eslint/css-tree/dist/csstree.js"></script>
<script src="https://unpkg.com/@eslint/css-tree/dist/csstree.js"></script>
MIT
main- the default branch for new development in the fork repoupstream- kept in sync withcsstree/csstree
When merging in changes from csstree/csstree, sync upstream in the GitHub UI (if possible). Then send a pull request to main to work through any merge conflicts.