CSS Property Parser

A comprehensive TypeScript library for parsing and serializing CSS property values with full MDN specification compliance.

🌐 Try the Interactive Demo →

Test all CSS property parsers live in your browser with real-time parsing and examples.

🚀 Features

• 124 CSS Property Evaluators - Complete parsing support for layout, typography, colors, and more
• Dual Package Support - Works with both ESM (import) and CommonJS (require)
• MDN Compliant - Follows official CSS specifications exactly
• TypeScript First - Full type safety with comprehensive type definitions for all CSS values
• Round-Trip Stable - Parse → serialize → parse produces identical results
• CSS Functions - Supports calc(), min(), max(), clamp(), gradients, and more
• CSS Variables - Handles custom properties with fallback values
• SPX Units - Supports Wix's SPX (Scalable-Pixel) units alongside standard CSS units
• Performance Optimized - Fast parsing with minimal memory footprint
• 8,428+ Tests - Comprehensive test coverage across 132 test suites with 100% pass rate
• Shared Evaluator Pattern - 95% code reduction through intelligent code reuse

📦 Installation

npm install @wix/css-property-parser

🎯 Usage

ESM (Import) - Recommended

import { Width, Height, Margin, Background, Font } from '@wix/css-property-parser';

// Parse CSS values
const width = Width.parse('calc(100% - 20px)');
const background = Background.parse('linear-gradient(45deg, red, blue)');

// Serialize back to CSS
const widthCSS = Width.toCSSValue(width);     // "calc(100% - 20px)"
const bgCSS = Background.toCSSValue(background); // "linear-gradient(45deg, red, blue)"

CommonJS (Require)

const { Width, Height, Margin, Background, Font } = require('@wix/css-property-parser');

// Parse CSS values
const width = Width.parse('calc(100% - 20px)');
const background = Background.parse('linear-gradient(45deg, red, blue)');

// Serialize back to CSS
const widthCSS = Width.toCSSValue(width);     // "calc(100% - 20px)"
const bgCSS = Background.toCSSValue(background); // "linear-gradient(45deg, red, blue)"

TypeScript Types

import { 
  Width, Height, Background, Font, Margin, Color, Position,
  // Import types for parsed values
  WidthValue, HeightValue, BackgroundValue, FontValue, MarginValue,
  ColorValue, PositionValue, LengthPercentageValue,
  // Import atomic types
  CSSLengthValue, CSSPercentageValue, LengthValue, PercentageValue
} from '@wix/css-property-parser';

// Use types for variables
const width: WidthValue | null = Width.parse('100px');
const background: BackgroundValue | null = Background.parse('red');
const margin: MarginValue | null = Margin.parse('10px 20px');
const color: ColorValue | null = Color.parse('#ff0000');
const position: PositionValue | null = Position.parse('absolute');

// Type-safe functions
function processWidth(value: string): WidthValue | null {
  return Width.parse(value);
}

function serializeFont(font: FontValue): string {
  return Font.toCSSValue(font) || '';
}

// All types are available from the main package for convenience
// This includes both property value types and atomic CSS types

🎯 Advanced Examples

Note: All examples work with both ESM (import) and CommonJS (require). For TypeScript type imports, see Usage section above.

import { Width, Height, Margin, Background, Font } from '@wix/css-property-parser';

// Parse CSS values with advanced features
const width = Width.parse('calc(100% - 20px)');
const height = Height.parse('50vh');
const margin = Margin.parse('10spx 20spx');  // SPX (Scalable-Pixel) support
const background = Background.parse('linear-gradient(45deg, red, blue)');
const font = Font.parse('bold 16px/1.5 "Helvetica Neue", Arial, sans-serif');

// Serialize back to CSS
const widthCSS = Width.toCSSValue(width);     // "calc(100% - 20px)"
const heightCSS = Height.toCSSValue(height);  // "50vh"
const marginCSS = Margin.toCSSValue(margin);  // "10spx 20spx"
const bgCSS = Background.toCSSValue(background); // "linear-gradient(45deg, red, blue)"
const fontCSS = Font.toCSSValue(font);        // "bold 16px/1.5 "Helvetica Neue", Arial, sans-serif"

📋 API Reference

Core API Pattern

Every property evaluator follows the same consistent API:

interface PropertyEvaluator<T> {
  parse(value: string): T | null;
  toCSSValue(parsed: T | null): string | null;
}

Property Evaluators

Layout Properties

import { Width, Height, MinWidth, MaxWidth, MinHeight, MaxHeight } from '@wix/css-property-parser';

// Sizing properties support lengths, percentages, and keywords
const width = Width.parse('50%');        // { value: 50, unit: '%' }
const height = Height.parse('auto');     // { keyword: 'auto' }
const minWidth = MinWidth.parse('0');    // { value: 0, unit: 'px' }

Spacing Properties

import { Margin, Padding, Gap, ColumnGap, RowGap } from '@wix/css-property-parser';

// Shorthand properties expand to constituent parts
const margin = Margin.parse('10px 20px');    // Expands to top/right/bottom/left
const padding = Padding.parse('1em');        // Expands to all sides
const gap = Gap.parse('10px 20px');         // Row and column gaps

Typography Properties

import { FontSize, FontWeight, FontFamily, LineHeight, LetterSpacing } from '@wix/css-property-parser';

// Font properties with comprehensive keyword support
const fontSize = FontSize.parse('1.2em');           // { type: 'length', value: 1.2, unit: 'em' }
const fontWeight = FontWeight.parse('bold');        // { type: 'keyword', keyword: 'bold' }
const fontFamily = FontFamily.parse('Arial, sans-serif'); // { type: 'font-list', families: ['Arial', 'sans-serif'] }
const lineHeight = LineHeight.parse('1.5');         // { type: 'number', value: 1.5 } (unitless)

Complex Properties

import { Background, Border, Font, TextShadow } from '@wix/css-property-parser';

// Multi-value and shorthand properties
const background = Background.parse('url(bg.jpg) no-repeat center / cover');
const border = Border.parse('2px solid red');
const font = Font.parse('bold 16px/1.4 "Helvetica Neue", Arial, sans-serif');
const textShadow = TextShadow.parse('2px 2px 4px rgba(0,0,0,0.5)');

Type Evaluators

For parsing individual CSS data types:

import { 
  LengthEvaluator, 
  PercentageEvaluator, 
  Color, 
  AngleEvaluator,
  NumberEvaluator 
} from '@wix/css-property-parser';

// Parse individual CSS types
const length = LengthEvaluator.parse('10px');        // { value: 10, unit: 'px' }
const percentage = PercentageEvaluator.parse('50%');  // { value: 50, unit: '%' }
const color = Color.parse('#ff0000');                // { type: 'hex', value: 'ff0000' }
const angle = AngleEvaluator.parse('45deg');         // { value: 45, unit: 'deg' }

🔧 Advanced Usage

CSS Variables

import { Width, CssVariable } from '@wix/css-property-parser';

// CSS variables are parsed but not resolved
const width = Width.parse('var(--main-width)');
// Returns: { CSSvariable: '--main-width' }

const widthWithFallback = Width.parse('var(--main-width, 100px)');
// Returns: { CSSvariable: '--main-width', defaultValue: '100px' }

CSS Functions

import { Width, FontSize } from '@wix/css-property-parser';

// Calc expressions
const width = Width.parse('calc(100% - 20px)');
// Returns: { expression: '100% - 20px', function: 'calc' }

// Min/max/clamp functions
const fontSize = FontSize.parse('clamp(1rem, 2.5vw, 2rem)');
// Returns: { expression: '1rem, 2.5vw, 2rem', function: 'clamp' }

Round-Trip Stability

import { Background } from '@wix/css-property-parser';

const originalValue = 'linear-gradient(45deg, red 0%, blue 100%)';
const parsed = Background.parse(originalValue);
const serialized = Background.toCSSValue(parsed);

console.log(serialized === originalValue); // true

🎨 Use Cases

Design Systems

import { FontSize, Color, Margin } from '@wix/css-property-parser';

// Validate design tokens
function validateDesignToken(property: string, value: string): boolean {
  switch (property) {
    case 'font-size':
      return FontSize.parse(value) !== null;
    case 'color':
      return Color.parse(value) !== null;
    case 'margin':
      return Margin.parse(value) !== null;
    default:
      return false;
  }
}

CSS-in-JS Libraries

import { Width, Height, Background } from '@wix/css-property-parser';

// Parse and transform CSS values
function processStyles(styles: Record<string, string>) {
  const processed: Record<string, any> = {};
  
  for (const [property, value] of Object.entries(styles)) {
    switch (property) {
      case 'width':
        processed.width = Width.parse(value);
        break;
      case 'height':
        processed.height = Height.parse(value);
        break;
      case 'background':
        processed.background = Background.parse(value);
        break;
    }
  }
  
  return processed;
}

CSS Optimization Tools

import { Color, Background } from '@wix/css-property-parser';

// Optimize CSS values
function optimizeColor(value: string): string {
  const parsed = Color.parse(value);
  if (parsed && parsed.type === 'hex') {
    // Convert to shortest hex format
    return Color.toCSSValue(parsed);
  }
  return value;
}

📚 Documentation

• Evaluator Guide - Comprehensive guide for creating new property evaluators
• Pre-Commit Hook - Development workflow automation

🧪 Testing

# Run all tests
npm test

# Run tests for specific property
npm test -- width.test.ts

# Run tests with coverage
npm test:coverage

# Watch mode for development
npm test:watch

🏗️ Development

# Install dependencies
npm install

# Build TypeScript
npm run build

# Build with watch mode
npm run build:watch

# Run development server
npm run dev

📊 Supported Properties

Total: 124 CSS Property Evaluators - All evaluators include full MDN compliance, comprehensive test coverage, and TypeScript type definitions.

💡 Quick Reference: Use {PropertyName}.parse(value) to parse and {PropertyName}.toCSSValue(parsed) to serialize any property below.

🔧 Data Types & Base Types (10 evaluators)

• Primitive Types: angle, color, length, number, percentage, string, time
• Composite Types: length-percentage, css-variable, blend-mode

📐 Sizing Properties (12 evaluators)

• Standard Box Model: width, height, min-width, max-width, min-height, max-height
• CSS Logical Properties: block-size, inline-size, min-block-size, max-block-size, min-inline-size, max-inline-size

📏 Spacing Properties (17 evaluators)

• Gap Properties (3): gap, column-gap, row-gap
• Margin Properties (7): margin (shorthand), margin-top, margin-right, margin-bottom, margin-left, margin-inline-start, margin-inline-end
• Padding Properties (7): padding (shorthand), padding-top, padding-right, padding-bottom, padding-left, padding-inline-start, padding-inline-end

🔲 Border Properties (43 evaluators)

• Border Shorthands (4): border, border-color, border-style, border-width
• Border Radius (5): border-radius, border-start-start-radius, border-start-end-radius, border-end-start-radius, border-end-end-radius
• Physical Borders (16):
  • Shorthands: border-top, border-right, border-bottom, border-left
  • Colors: border-top-color, border-right-color, border-bottom-color, border-left-color
  • Styles: border-top-style, border-right-style, border-bottom-style, border-left-style
  • Widths: border-top-width, border-right-width, border-bottom-width, border-left-width
• CSS Logical Block Borders (9):
  • Shorthands: border-block, border-block-start, border-block-end
  • Colors: border-block-start-color, border-block-end-color
  • Styles: border-block-start-style, border-block-end-style
  • Widths: border-block-start-width, border-block-end-width
• CSS Logical Inline Borders (9):
  • Shorthands: border-inline, border-inline-start, border-inline-end
  • Colors: border-inline-start-color, border-inline-end-color
  • Styles: border-inline-start-style, border-inline-end-style
  • Widths: border-inline-start-width, border-inline-end-width

🔤 Typography Properties (18 evaluators)

• Font Properties (7): font (shorthand), font-family, font-size, font-weight, font-style, font-variant, font-stretch
• Text Properties (6): text-align, text-transform, text-decoration, text-shadow, text-overflow, text-indent
• Text Spacing (2): line-height, letter-spacing
• Text Flow (4): white-space, word-break, overflow-wrap, writing-mode

🏗️ Layout & Grid Properties (12 evaluators)

• CSS Grid Template (3): grid-template (shorthand), grid-template-columns, grid-template-rows
• CSS Grid Areas (3): grid-area, grid-column, grid-row
• CSS Grid Gaps (3): grid-gap (shorthand), grid-column-gap, grid-row-gap
• Layout Control (3): display, overflow, visibility

🎨 Visual Properties (8 evaluators)

• Colors & Effects (4): background, color, opacity, box-shadow
• Object Properties (2): object-fit, object-position
• Positioning (2): position, z-index

⚡ Layout Alignment (4 evaluators)

• Flexbox & Grid Alignment (4): align-items, align-self, justify-content, flex-direction

🔄 Advanced Features

• Shared Evaluator Pattern (8 shared): 95% code reduction through intelligent reuse

  • Sizing properties: width/height variants
  • Spacing properties: gap, margin, padding variants
  • Border width properties: all border-width variants
  • Border style properties: all border-style variants
  • Border color properties: all border-color variants
  • Border individual properties: border shorthand variants
  • Logical border properties: block/inline border variants
  • Logical border radius properties: corner radius variants

• CSS Functions: Full support for calc(), min(), max(), clamp(), var(), gradients

• SPX Units: Wix Scalable-Pixel units for responsive design

• Round-Trip Stability: Parse → serialize → parse produces identical results

• Performance: Optimized parsing with minimal memory footprint

🤝 Contributing

1. Fork the repository
2. Create a feature branch
3. Add comprehensive tests (20+ tests minimum)
4. Ensure all tests pass
5. Follow the Evaluator Guide
6. Submit a pull request

📄 License

ISC License - see LICENSE file for details.

🙏 Acknowledgments

• Built with MDN CSS specifications as the authoritative reference
• Inspired by the need for robust CSS parsing in modern web applications
• Comprehensive testing ensures production-ready reliability
• Enhanced and documented with assistance from Claude (Anthropic AI)

📋 Complete Evaluator Exports Reference

All evaluators are available as named exports from the main package. Use import { EvaluatorName } from '@wix/css-property-parser' or const { EvaluatorName } = require('@wix/css-property-parser').

🔧 Type & Utility Evaluators

| Export Name | CSS Property/Type | Description | |-------------|-------------------|-------------| | AngleEvaluator | <angle> | CSS angle values (deg, rad, turn, grad) | | BlendMode | mix-blend-mode, background-blend-mode | CSS blend mode keywords | | Color | <color> | CSS color values (hex, rgb, hsl, named, etc.) | | CssVariable | var() | CSS custom properties and variables | | LengthEvaluator | <length> | CSS length values (px, em, rem, vh, etc.) | | LengthPercentage | <length-percentage> | Combined length and percentage values | | NumberEvaluator | <number> | CSS numeric values | | PercentageEvaluator | <percentage> | CSS percentage values | | Position | position | CSS position keywords (static, relative, absolute, fixed, sticky) | | StringEvaluator | <string> | CSS string values | | TimeEvaluator | <time> | CSS time values (s, ms) |

📐 Sizing Properties

| Export Name | CSS Property | Description | |-------------|--------------|-------------| | BlockSize | block-size | Logical block dimension | | Height | height | Element height | | InlineSize | inline-size | Logical inline dimension | | MaxBlockSize | max-block-size | Maximum logical block size | | MaxHeight | max-height | Maximum element height | | MaxInlineSize | max-inline-size | Maximum logical inline size | | MaxWidth | max-width | Maximum element width | | MinBlockSize | min-block-size | Minimum logical block size | | MinHeight | min-height | Minimum element height | | MinInlineSize | min-inline-size | Minimum logical inline size | | MinWidth | min-width | Minimum element width | | Width | width | Element width |

📏 Spacing Properties

| Export Name | CSS Property | Description | |-------------|--------------|-------------| | ColumnGap | column-gap | Gap between columns | | Gap | gap | Gap shorthand (row and column) | | Margin | margin | Margin shorthand (all sides) | | MarginBottom | margin-bottom | Bottom margin | | MarginInlineEnd | margin-inline-end | Logical inline end margin | | MarginInlineStart | margin-inline-start | Logical inline start margin | | MarginLeft | margin-left | Left margin | | MarginRight | margin-right | Right margin | | MarginTop | margin-top | Top margin | | Padding | padding | Padding shorthand (all sides) | | PaddingBottom | padding-bottom | Bottom padding | | PaddingInlineEnd | padding-inline-end | Logical inline end padding | | PaddingInlineStart | padding-inline-start | Logical inline start padding | | PaddingLeft | padding-left | Left padding | | PaddingRight | padding-right | Right padding | | PaddingTop | padding-top | Top padding | | RowGap | row-gap | Gap between rows |

🔲 Border Properties

| Export Name | CSS Property | Description | |-------------|--------------|-------------| | Border | border | Border shorthand (all sides) | | BorderBlock | border-block | Logical block borders | | BorderBlockEnd | border-block-end | Logical block end border | | BorderBlockEndColor | border-block-end-color | Logical block end border color | | BorderBlockEndStyle | border-block-end-style | Logical block end border style | | BorderBlockEndWidth | border-block-end-width | Logical block end border width | | BorderBlockStart | border-block-start | Logical block start border | | BorderBlockStartColor | border-block-start-color | Logical block start border color | | BorderBlockStartStyle | border-block-start-style | Logical block start border style | | BorderBlockStartWidth | border-block-start-width | Logical block start border width | | BorderBottom | border-bottom | Bottom border | | BorderBottomColor | border-bottom-color | Bottom border color | | BorderBottomStyle | border-bottom-style | Bottom border style | | BorderBottomWidth | border-bottom-width | Bottom border width | | BorderColor | border-color | Border color shorthand | | BorderEndEndRadius | border-end-end-radius | Logical end-end corner radius | | BorderEndStartRadius | border-end-start-radius | Logical end-start corner radius | | BorderInline | border-inline | Logical inline borders | | BorderInlineEnd | border-inline-end | Logical inline end border | | BorderInlineEndColor | border-inline-end-color | Logical inline end border color | | BorderInlineEndStyle | border-inline-end-style | Logical inline end border style | | BorderInlineEndWidth | border-inline-end-width | Logical inline end border width | | BorderInlineStart | border-inline-start | Logical inline start border | | BorderInlineStartColor | border-inline-start-color | Logical inline start border color | | BorderInlineStartStyle | border-inline-start-style | Logical inline start border style | | BorderInlineStartWidth | border-inline-start-width | Logical inline start border width | | BorderLeft | border-left | Left border | | BorderLeftColor | border-left-color | Left border color | | BorderLeftStyle | border-left-style | Left border style | | BorderLeftWidth | border-left-width | Left border width | | BorderRadius | border-radius | Border radius shorthand | | BorderRight | border-right | Right border | | BorderRightColor | border-right-color | Right border color | | BorderRightStyle | border-right-style | Right border style | | BorderRightWidth | border-right-width | Right border width | | BorderStartEndRadius | border-start-end-radius | Logical start-end corner radius | | BorderStartStartRadius | border-start-start-radius | Logical start-start corner radius | | BorderStyle | border-style | Border style shorthand | | BorderTop | border-top | Top border | | BorderTopColor | border-top-color | Top border color | | BorderTopStyle | border-top-style | Top border style | | BorderTopWidth | border-top-width | Top border width | | BorderWidth | border-width | Border width shorthand |

🔤 Typography Properties

| Export Name | CSS Property | Description | |-------------|--------------|-------------| | Font | font | Font shorthand (family, size, weight, style, etc.) | | FontFamily | font-family | Font family stack | | FontSize | font-size | Font size | | FontStretch | font-stretch | Font stretch/width | | FontStyle | font-style | Font style (normal, italic, oblique) | | FontVariant | font-variant | Font variant settings | | FontWeight | font-weight | Font weight (normal, bold, 100-900) | | LetterSpacing | letter-spacing | Spacing between characters | | LineHeight | line-height | Line height/leading | | TextAlign | text-align | Text alignment | | TextDecoration | text-decoration | Text decoration (underline, strikethrough, etc.) | | TextIndent | text-indent | First-line text indentation | | TextOverflow | text-overflow | Text overflow behavior | | TextShadow | text-shadow | Text shadow effects | | TextTransform | text-transform | Text case transformation | | WhiteSpace | white-space | Whitespace handling | | WordBreak | word-break | Word breaking behavior | | WritingMode | writing-mode | Text writing direction |

🏗️ Layout & Grid Properties

| Export Name | CSS Property | Description | |-------------|--------------|-------------| | Display | display | Display type (block, inline, flex, grid, etc.) | | GridArea | grid-area | Grid area placement | | GridColumn | grid-column | Grid column placement | | GridColumnGap | grid-column-gap | Gap between grid columns | | GridGap | grid-gap | Grid gap shorthand | | GridRow | grid-row | Grid row placement | | GridRowGap | grid-row-gap | Gap between grid rows | | GridTemplate | grid-template | Grid template shorthand | | GridTemplateColumns | grid-template-columns | Grid column track definitions | | GridTemplateRows | grid-template-rows | Grid row track definitions | | Overflow | overflow | Content overflow behavior | | OverflowWrap | overflow-wrap | Long word wrapping behavior |

🎨 Visual Properties

| Export Name | CSS Property | Description | |-------------|--------------|-------------| | Background | background | Background shorthand (image, color, position, etc.) | | BoxShadow | box-shadow | Box shadow effects | | ObjectFit | object-fit | Object fitting behavior | | ObjectPosition | object-position | Object positioning | | Opacity | opacity | Element opacity/transparency | | Visibility | visibility | Element visibility | | ZIndex | z-index | Stacking order |

⚡ Layout Alignment

| Export Name | CSS Property | Description | |-------------|--------------|-------------| | AlignItems | align-items | Cross-axis alignment | | AlignSelf | align-self | Individual item cross-axis alignment | | FlexDirection | flex-direction | Flex container direction | | JustifyContent | justify-content | Main-axis alignment |

Total: 124 Evaluator Exports - All evaluators follow the same API pattern: parse(value: string) and toCSSValue(parsed) with full TypeScript support.