@wix/css-property-parser

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

• 123 CSS Property Evaluators - Complete parsing support for layout, typography, colors, and more
• MDN Compliant - Follows official CSS specifications exactly
• TypeScript First - Full type safety with comprehensive type definitions
• 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
• 8,331+ 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

🎯 Quick Start

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

// Parse CSS values
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)');

// 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)"

📋 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: 123 CSS Property Evaluators

Data Types & Base Types (10 evaluators)

• angle, blend-mode, color, css-variable, length, length-percentage
• number, percentage, string, time

Sizing Properties (12 evaluators)

• Standard Box: width, height, min-width, max-width, min-height, max-height
• Logical Sizing: block-size, inline-size, min-block-size, max-block-size, min-inline-size, max-inline-size

Spacing Properties (17 evaluators)

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

Border Properties (43 evaluators)

• Main Border: border, border-color, border-style, border-width
• Border Radius: border-radius, border-start-start-radius, border-start-end-radius, border-end-start-radius, border-end-end-radius
• Physical Borders: border-top, border-right, border-bottom, border-left
• Physical Border Colors: border-top-color, border-right-color, border-bottom-color, border-left-color
• Physical Border Styles: border-top-style, border-right-style, border-bottom-style, border-left-style
• Physical Border Widths: border-top-width, border-right-width, border-bottom-width, border-left-width
• Logical Block Borders: border-block, border-block-start, border-block-end
• Logical Block Colors: border-block-start-color, border-block-end-color
• Logical Block Styles: border-block-start-style, border-block-end-style
• Logical Block Widths: border-block-start-width, border-block-end-width
• Logical Inline Borders: border-inline, border-inline-start, border-inline-end
• Logical Inline Colors: border-inline-start-color, border-inline-end-color
• Logical Inline Styles: border-inline-start-style, border-inline-end-style
• Logical Inline Widths: border-inline-start-width, border-inline-end-width

Typography Properties (18 evaluators)

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

Layout & Grid Properties (12 evaluators)

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

Visual Properties (8 evaluators)

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

Layout Alignment (4 evaluators)

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

Shared Evaluators (8 shared)

• Sizing Properties: Shared evaluator for width/height variants (95% code reduction)
• Spacing Properties: Shared evaluators for gap, margin, padding variants
• Border Width Properties: Shared evaluator for border-width variants
• Border Style Properties: Shared evaluator for border-style variants
• Border Color Properties: Shared evaluator for border-color variants
• Border Individual Properties: Shared evaluator for border shorthand variants

🤝 Contributing

• Fork the repository
• Create a feature branch
• Add comprehensive tests (20+ tests minimum)
• Ensure all tests pass
• Follow the Evaluator Guide
• 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)