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Pattern matching allows you to automatically highlight text based on regular expressions or word lists. This is ideal for syntax highlighting, keyword detection, or finding specific patterns in user input.

​
Pattern-based highlighting

The HighlightBuilder.pattern() method searches text using a regular expression and returns character range highlights for all matches: 
import { DyeLight, HighlightBuilder } from 'dyelight';

function CodeEditor() {
  const [code, setCode] = useState(`function hello() {
  const message = "Hello World";
  console.log(message);
}`);

  // Highlight JavaScript keywords
  const keywordHighlights = HighlightBuilder.pattern(
    code,
    /\b(function|const|let|var|if|else|for|while)\b/g,
    'text-blue-600 font-semibold'
  );

  return (
    <DyeLight
      value={code}
      onChange={setCode}
      highlights={keywordHighlights}
    />
  );
}
The pattern is automatically converted to a global regex (/g flag) if not already present. This ensures all matches in the text are found, not just the first one (see builder.ts:86).

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Pattern method signature

HighlightBuilder.pattern(
  text: string,              // The text to search within
  pattern: RegExp | string,  // Regex pattern or string to convert to regex
  className?: string,        // Optional CSS class for matches
  style?: React.CSSProperties // Optional inline styles
)

​
Common regex patterns

Here are some useful patterns for different use cases:

​
Email addresses

const emailHighlights = HighlightBuilder.pattern(
  text,
  /\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b/g,
  'email-highlight'
);

​
URLs

const urlHighlights = HighlightBuilder.pattern(
  text,
  /https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)/g,
  'text-blue-500 underline'
);

​
Phone numbers

const phoneHighlights = HighlightBuilder.pattern(
  text,
  /\b\d{3}[-.]?\d{3}[-.]?\d{4}\b/g,
  'bg-green-100'
);

​
String literals (quoted text)

const stringHighlights = HighlightBuilder.pattern(
  code,
  /"[^"]*"/g,
  'text-green-600'
);

​
Word-based highlighting

The HighlightBuilder.words() method is a specialized version of pattern matching that highlights complete words from a list: 
function KeywordHighlighter() {
  const [code, setCode] = useState('function test() { return null; }');

  // Highlight specific programming keywords
  const highlights = HighlightBuilder.words(
    code,
    ['function', 'const', 'let', 'var', 'return'],
    'keyword'
  );

  return (
    <DyeLight
      value={code}
      onChange={setCode}
      highlights={highlights}
      className="font-mono"
    />
  );
}

​
How it works

Under the hood, words() creates a word-boundary regex pattern from your word list (see builder.ts:161-163): 
// This:
HighlightBuilder.words(text, ['TODO', 'FIXME', 'NOTE'], 'highlight');

// Becomes:
HighlightBuilder.pattern(text, /\b(TODO|FIXME|NOTE)\b/g, 'highlight');
The word boundaries (\b) ensure that only complete words are matched. For example, searching for “log” won’t match “blog” or “logger”.

​
Combining multiple patterns

You can combine highlights from multiple pattern searches: 
function SyntaxHighlighter() {
  const [code, setCode] = useState(`
function hello() {
  const message = "Hello World";
  console.log(message);
}
  `);

  // Highlight different syntax elements
  const keywords = HighlightBuilder.pattern(
    code,
    /\b(function|const|let|var|if|else|for|while)\b/g,
    'text-blue-600 font-semibold'
  );

  const strings = HighlightBuilder.pattern(
    code,
    /"[^"]*"/g,
    'text-green-600'
  );

  const functions = HighlightBuilder.words(
    code,
    ['console', 'log'],
    'text-purple-600'
  );

  return (
    <DyeLight
      value={code}
      onChange={setCode}
      highlights={[...keywords, ...strings, ...functions]}
      className="font-mono text-sm"
      enableAutoResize
    />
  );
}

​
Styling pattern matches

You can use either CSS classes or inline styles with patterns:

​
CSS classes

const highlights = HighlightBuilder.pattern(
  text,
  /\bTODO\b/g,
  'todo-highlight'
);

.todo-highlight {
  background-color: orange;
  color: white;
  font-weight: bold;
  padding: 0 4px;
  border-radius: 2px;
}

​
Inline styles

const highlights = HighlightBuilder.pattern(
  text,
  /\bERROR\b/g,
  undefined,
  {
    backgroundColor: 'red',
    color: 'white',
    fontWeight: 'bold',
    textDecoration: 'underline wavy red',
  }
);

​
Case-insensitive matching

To perform case-insensitive pattern matching, add the i flag to your regex: 
const highlights = HighlightBuilder.pattern(
  text,
  /\btodo\b/gi,  // The 'i' flag makes it case-insensitive
  'todo-highlight'
);
When passing a string pattern, you can create a RegExp with flags:
const pattern = new RegExp('todo', 'gi');
const highlights = HighlightBuilder.pattern(text, pattern, 'highlight');

​
Performance with patterns

Pattern matching uses JavaScript’s native String.matchAll() method (see builder.ts:87), which is highly optimized. However, for very large documents or complex patterns:
  • Memoize pattern results when the text hasn’t changed:
const highlights = useMemo(
  () => HighlightBuilder.pattern(code, /\bfunction\b/g, 'keyword'),
  [code]
);
  • Debounce pattern matching during rapid text input:
const [text, setText] = useState('');
const debouncedText = useDebounce(text, 300);

const highlights = useMemo(
  () => HighlightBuilder.pattern(debouncedText, pattern, className),
  [debouncedText]
);
For syntax highlighting multiple patterns simultaneously, compute all highlights in a single useMemo to avoid redundant processing.

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