unescape static method

String? unescape(String? htmlText)

Converts HTML entities to their corresponding characters.

Handles both named entities (e.g., &, <,  ) and numeric entities (e.g., A, A).

Returns null if the input is null or empty.

Supported named entities include:

• Basic: &, <, >, ", ', '
• Whitespace:  
• Symbols: ©, ®, ™, •, …
• Currency: €, £, ¥, ¢
• Punctuation: –, —, ‘, ’, “, ”
• Math: ×, ÷, ±, ½, ¼, ¾
• And more...

Example:

HtmlUtils.unescape('&lt;div&gt;'); // '<div>'
HtmlUtils.unescape('&amp;amp;'); // '&amp;'
HtmlUtils.unescape('&#65;'); // 'A'
HtmlUtils.unescape('&#x41;'); // 'A'
HtmlUtils.unescape('Hello&nbsp;World'); // 'Hello World'
HtmlUtils.unescape('&copy; 2024'); // '© 2024'

Implementation

static String? unescape(String? htmlText) {
  if (htmlText == null || htmlText.isEmpty) {
    return null;
  }

  String result = htmlText;

  // Replace named entities
  _htmlEntities.forEach((String entity, String char) {
    result = result.replaceAll(entity, char);
  });

  // Replace numeric entities (decimal and hex)
  result = result.replaceAllMapped(_numericEntityRegex, (Match match) {
    final String? decimal = match.group(1);
    final String? hex = match.group(2);

    int? codePoint;
    if (decimal != null) {
      codePoint = int.tryParse(decimal);
    } else if (hex != null) {
      codePoint = int.tryParse(hex, radix: 16);
    }

    if (codePoint != null && codePoint > 0 && codePoint <= 0x10FFFF) {
      return String.fromCharCode(codePoint);
    }
    return match.group(0) ?? ''; // Return original if invalid
  });

  return result;
}