css-tree
Advanced tools
Package description
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.
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 }));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 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 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 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.
Changelog
1.0.0-alpha.27 (January 14, 2018)
generate() methods invocation, methods now take a node as a single argument and context (i.e. this) that have methods: chunk(), node() and children()translate() to generate() and changed to take options argumenttranslateMarkup(ast, enter, leave) method, use generate(ast, { decorator: (handlers) => { ... }}) insteadtranslateWithSourceMap(ast), use generate(ast, { sourceMap: true }) insteadwalk() to take an options argument instead of handler, with enter, leave, visit and reverse options (walk(ast, fn) is still works and equivalent to walk(ast, { enter: fn }))walkUp(ast, fn), use walk(ast, { leave: fn })walkRules(ast, fn), use walk(ast, { visit: 'Rule', enter: fn }) insteadwalkRulesRight(ast, fn), use walk(ast, { visit: 'Rule', reverse: true, enter: fn }) insteadwalkDeclarations(ast, fn), use walk(ast, { visit: 'Declaration', enter: fn }) insteadreverse: true will fail on arrays since they have no forEachRight() method)List#forEach() methodList#forEachRight() methodList#filter() methodList#map() method to return a List instance instead of ArrayList#push() method, similar to List#appendData() but returns nothingList#pop() methodList#unshift() method, similar to List#prependData() but returns nothingList#shift() methodList#prependList() methodList#insert(), List#insertData(), List#appendList() and List#insertList() methods to return a list that performed an operationkeyword() method
name field to include a vendor prefixbasename field to contain a name without a vendor prefixcustom field that contain a true when keyword is a custom property referenceproperty() method
name field to include a vendor prefixbasename field to contain a name without any prefixes, i.e. a hack and a vendor prefixvendorPrefix() methodisCustomProperty() methodReadme
CSSTree is a tool set to work with CSS, including fast detailed parser (string->AST), walker (AST traversal), generator (AST->string) and lexer (validation and matching) based on knowledge of spec 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.
NOTE: The project is in alpha stage since some parts need further improvements, AST format and API are subjects to change. However it's stable enough and used by packages like CSSO (CSS minifier) and SVGO (SVG optimizer) in production.
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 declarations for component parts.
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 the special nodes, which 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.
Syntax validation
The build-in lexer can test CSS against syntaxes defined by W3C. CSSTree uses mdn/data as a basis for lexer's dictionaries and extends them with vendor specific and legacy syntaxes. Lexer can only check the declaration values currently, but this feature will be extended to other parts of the CSS in the future.
Install with npm:
> npm install css-tree
Use in your code:
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.generate(ast));
// .hello{world:"!"}
MIT
FAQs
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 npm package css-tree receives a total of 22,688,665 weekly downloads. As such, css-tree popularity was classified as popular.
We found that css-tree demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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