CSS parser and minifier for node and the browser
$ npm install @tbela99/css-parser- no dependency
- fault-tolerant parser, will try to fix invalid tokens according to the CSS syntax module 3 recommendations.
- efficient minification without unsafe transforms, see benchmark
- minify colors.
- support css color level 4 & 5: color(), lab(), lch(), oklab(), oklch(), color-mix() and relative color
- generate nested css rules
- convert nested css rules to legacy syntax
- generate sourcemap
- compute css shorthands. see supported properties list below
- evaluate calc()
- inline css variables
- remove duplicate properties
- flatten @import rules
There are several ways to import the library into your application.
import as a module
import {transform} from '@tbela99/css-parser';
// ...import as a module
import {transform} from 'npm:@tbela99/css-parser';
// ...import as a CommonJS module
const {transform} = require('@tbela99/css-parser/cjs');
// ...Programmatic import
import {transform} from '@tbela99/css-parser/web';
// ...Javascript module from cdn
<script type="module">
import {transform} from 'https://esm.sh/@tbela99/css-parser@0.4.0/web';
const css = `
.s {
background: color-mix(in hsl, color(display-p3 0 1 0) 80%, yellow);
}
`;
console.debug(await transform(css).then(r => r.code));
</script>Javascript module
<script src="dist/web/index.js" type="module"></script>Single Javascript file
<script src="dist/index-umd-web.js"></script>Parse and render css in a single pass.
transform(css, transformOptions: TransformOptions = {}): TransformResultimport {transform} from '@tbela99/css-parser';
const {ast, code, map, errors, stats} = await transform(css, {minify: true, resolveImport: true, cwd: 'files/css'});Include ParseOptions and RenderOptions
Minify Options
- minify: boolean, optional. default to true. optimize ast.
- nestingRules: boolean, optional. automatically generated nested rules.
- expandNestingRules: boolean, optional. convert nesting rules into separate rules. will automatically set nestingRules to false.
- removeDuplicateDeclarations: boolean, optional. remove duplicate declarations.
- computeShorthand: boolean, optional. compute shorthand properties.
- inlineCssVariables: boolean, optional. replace css variables with their current value.
- computeCalcExpression: boolean, optional. evaluate calc() expression
- inlineCssVariables: boolean, optional. replace some css variables with their actual value. they must be declared once in the :root {} or html {} rule.
- removeEmpty: boolean, optional. remove empty rule lists from the ast.
Sourcemap Options
- src: string, optional. original css file location to be used with sourcemap.
- sourcemap: boolean, optional. preserve node location data.
Misc Options
- resolveUrls: boolean, optional. resolve css 'url()' according to the parameters 'src' and 'cwd'
- resolveImport: boolean, optional. replace @import rule by the content of its referenced stylesheet.
- removeCharset: boolean, optional. remove @charset.
- cwd: string, optional. the current working directory. when specified url() are resolved using this value
- visitor: VisitorNodeMap, optional. node visitor used to transform the ast.
- signal: AbortSignal, optional. abort parsing.
Minify Options
- minify: boolean, optional. default to true. minify css output.
- expandNestingRules: boolean, optional. expand nesting rules.
- preserveLicense: boolean, force preserving comments starting with '/*!' when minify is enabled.
- removeComments: boolean, remove comments in generated css.
- colorConvert: boolean, convert colors to hex.
Sourcemap Options
- sourcemap: boolean, optional. generate sourcemap
Misc Options
- indent: string, optional. css indention string. uses space character by default.
- newLine: string, optional. new line character.
- output: string, optional. file where to store css. url() are resolved according to the specified value. no file is created though.
- cwd: string, optional. value used as current working directory. when output is not provided, urls are resolved according to this value.
parse(css, parseOptions = {})const {ast, errors, stats} = await parse(css);render(ast, RenderOptions = {});Rendering ast
import {render} from '@tbela99/css-parser';
// minified
const {code, stats} = render(ast, {minify: true});
console.log(code);CSS
.clear {
width: 0;
height: 0;
color: transparent;
}
.clearfix:before {
height: 0;
width: 0;
}import {transform} from '@tbela99/css-parser';
const result = await transform(css);Result
.clear,.clearfix:before{height:0;width:0}.clear{color:#0000}CSS
const {parse, render} = require("@tbela99/css-parser/cjs");
const css = `
table.colortable td {
text-align:center;
}
table.colortable td.c {
text-transform:uppercase;
}
table.colortable td:first-child, table.colortable td:first-child+td {
border:1px solid black;
}
table.colortable th {
text-align:center;
background:black;
color:white;
}
`;
const result = await parse(css, {nestingRules:true}).then(result => render(result.ast, {minify:false}).code);Result
table.colortable {
& td {
text-align: center;
&.c {
text-transform: uppercase
}
&:first-child,&:first-child+td {
border: 1px solid #000
}
}
& th {
text-align: center;
background: #000;
color: #fff
}
}CSS
table.colortable {
& td {
text-align: center;
&.c {
text-transform: uppercase
}
&:first-child,&:first-child+td {
border: 1px solid #000
}
}
& th {
text-align: center;
background: #000;
color: #fff
}
}Javascript
import {parse, render} from '@tbela99/css-parser';
const options = {minify: true};
const {code} = await parse(css, options).then(result => render(result.ast, {minify: false, expandNestingRules: true}));
//
console.debug(code);Result
table.colortable td {
text-align:center;
}
table.colortable td.c {
text-transform:uppercase;
}
table.colortable td:first-child, table.colortable td:first-child+td {
border:1px solid black;
}
table.colortable th {
text-align:center;
background:black;
color:white;
}import {parse, render} from '@tbela99/css-parser';
const css = `
.foo-bar {
width: calc(100px * 2);
height: calc(((75.37% - 63.5px) - 900px) + (2 * 100px));
max-width: calc(3.5rem + calc(var(--bs-border-width) * 2));
}
`;
const prettyPrint = await parse(css).then(result => render(result.ast, {minify: false}).code);result
.foo-bar {
width: 200px;
height: calc(75.37% - 763.5px);
max-width: calc(3.5rem + var(--bs-border-width)*2)
}import {parse, render} from '@tbela99/css-parser';
const css = `
:root {
--preferred-width: 20px;
}
.foo-bar {
width: calc(calc(var(--preferred-width) + 1px) / 3 + 5px);
height: calc(100% / 4);}
`
const prettyPrint = await parse(css, {inlineCssVariables: true}).then(result => render(result.ast, {minify: false}).code);result
.foo-bar {
width: 12px;
height: 25%
}import {parse, render} from '@tbela99/css-parser';
const css = `
:root {
--color: green;
}
._19_u :focus {
color: hsl(from var(--color) calc(h * 2) s l);
}
`
const prettyPrint = await parse(css, {inlineCssVariables: true}).then(result => render(result.ast, {minify: false}).code);result
._19_u :focus {
color: navy
}import {walk} from '@tbela99/css-parser';
for (const {node, parent, root} of walk(ast)) {
// do something
}- typ: string 'Comment'
- val: string, the comment
- typ: string 'Declaration'
- nam: string, declaration name
- val: array of tokens
- typ: string 'Rule'
- sel: string, css selector
- chi: array of children
- typ: string 'AtRule'
- nam: string. AtRule name
- val: rule prelude
- typ: string 'Stylesheet'
- chi: array of children
- [x] sourcemap generation
- [x] reduce calc()
- [x] inline css variables
- [x] merge identical rules
- [x] merge adjacent rules
- [x] minify colors
- [x] minify numbers and Dimensions tokens
- [x] compute shorthand: see the list below
- [x] remove redundant declarations
- [x] conditionally unwrap :is()
- [x] automatic css nesting
- [x] automatically wrap selectors using :is()
- [x] avoid reparsing (declarations, selectors, at-rule)
- [x] node and browser versions
- [x] decode and replace utf-8 escape sequence
all- [x] animation
- [x] background
- [x] border
- [ ] border-block-end
- [ ] border-block-start
- [x] border-bottom
- [x] border-color
- [ ] border-image
- [ ] border-inline-end
- [ ] border-inline-start
- [x] border-left
- [x] border-radius
- [x] border-right
- [x] border-style
- [x] border-top
- [x] border-width
- [x] column-rule
- [x] columns
- [x] container
- [ ] contain-intrinsic-size
- [x] flex
- [x] flex-flow
- [x] font
- [ ] font-synthesis
- [ ] font-variant
- [x] gap
- [ ] grid
- [ ] grid-area
- [ ] grid-column
- [ ] grid-row
- [ ] grid-template
- [x] inset
- [x] list-style
- [x] margin
- [ ] mask
- [ ] offset
- [x] outline
- [x] overflow
- [x] padding
- [ ] place-content
- [ ] place-items
- [ ] place-self
- [ ] scroll-margin
- [ ] scroll-padding
- [ ] scroll-timeline
- [x] text-decoration
- [x] text-emphasis
- [x] transition
- [x] flatten @import
Ast can be transformed using node visitors
import {AstDeclaration, ParserOptions} from "../src/@types";
const options: ParserOptions = {
visitor: {
Declaration: (node: AstDeclaration) => {
if (node.nam == '-webkit-transform') {
node.nam = 'transform'
}
}
}
}
const css = `
.foo {
-webkit-transform: scale(calc(100 * 2/ 15));
}
`;
console.debug(await transform(css, options));
// .foo{transform:scale(calc(40/3))}import {AstDeclaration, LengthToken, ParserOptions} from "../src/@types";
import {EnumToken, EnumToken} from "../src/lib";
import {transform} from "../src/node";
const options: ParserOptions = {
visitor: {
Declaration: {
// called only for height declaration
height: (node: AstDeclaration): AstDeclaration[] => {
return [
node,
{
typ: EnumToken.DeclarationNodeType,
nam: 'width',
val: [
<LengthToken>{
typ: EnumToken.Length,
val: '3',
unit: 'px'
}
]
}
];
}
}
}
};
const css = `
.foo {
height: calc(100px * 2/ 15);
}
.selector {
color: lch(from peru calc(l * 0.8) calc(c * 0.7) calc(h + 180))
}
`;
console.debug(await transform(css, options));
// .foo{height:calc(40px/3);width:3px}.selector{color:#0880b0}import {AstAtRule, ParserOptions} from "../src/@types";
import {transform} from "../src/node";
const options: ParserOptions = {
visitor: {
AtRule: (node: AstAtRule): AstAtRule => {
if (node.nam == 'media') {
return {...node, val: 'all'}
}
}
}
};
const css = `
@media screen {
.foo {
height: calc(100px * 2/ 15);
}
}
`;
console.debug(await transform(css, options));
// .foo{height:calc(40px/3)}import {AstAtRule, ParserOptions} from "../src/@types";
import {transform} from "../src/node";
const options: ParserOptions = {
visitor: {
AtRule: {
media: (node: AstAtRule): AstAtRule => {
return {...node, val: 'all'}
}
}
}
};
const css = `
@media screen {
.foo {
height: calc(100px * 2/ 15);
}
}
`;
console.debug(await transform(css, options));
// .foo{height:calc(40px/3)}import {AstAtRule, ParserOptions} from "../src/@types";
import {transform} from "../src/node";
const options: ParserOptions = {
visitor: {
Rule (node: AstRule): AstRule {
return {...node, sel: '.foo,.bar,.fubar'};
}
}
};
const css = `
.foo {
height: calc(100px * 2/ 15);
}
`;
console.debug(await transform(css, options));
// .foo,.bar,.fubar{height:calc(40px/3)}Adding declarations
import {transform} from "../src/node";
import {AstRule, ParserOptions} from "../src/@types";
import {parseDeclarations} from "../src/lib";
const options: ParserOptions = {
removeEmpty: false,
visitor: {
Rule: async (node: AstRule): Promise<AstRule | null> => {
if (node.sel == '.foo') {
node.chi.push(...await parseDeclarations('width: 3px'));
return node;
}
return null;
}
}
};
const css = `
.foo {
}
`;
console.debug(await transform(css, options));
// .foo{width:3px}Thanks to Jetbrains for sponsoring this project with a free license