formatPercent function

String formatPercent(
  1. num value, {
  2. String? locale,
  3. int? decimalDigits = 0,
})

Formats a percentage value for locale in pure Dart.

Accepts ratio fractions between -1.0 and 1.0 (e.g. 0.42 becomes 42%) as well as whole percentage numbers (e.g. 42 becomes 42%). Includes appropriate locale spacing before the % symbol for languages such as French, German, Russian, and Swedish.

When locale is omitted, defaults to the active BloomI18n.instance.locale value.

formatPercent(0.42, locale: 'en-US'); // "42%"
formatPercent(0.42, locale: 'fr-FR'); // "42 %"

See also:

Implementation

String formatPercent(
  num value, {
  String? locale,
  int? decimalDigits = 0,
}) {
  final intlLocale =
      (locale ?? BloomI18n.instance.locale.value).replaceAll('-', '_');
  final percentValue = value <= 1.0 && value >= -1.0 ? value : value / 100;
  try {
    return intl.NumberFormat.decimalPercentPattern(
            locale: intlLocale, decimalDigits: decimalDigits)
        .format(percentValue);
  } catch (_) {
    // Fall back to the small built-in formatter for an unknown locale.
  }
  final loc = (locale ?? BloomI18n.instance.locale.value)
      .replaceAll('_', '-')
      .toLowerCase();
  final lang = loc.split('-').first;
  final fallbackPercentValue =
      value <= 1.0 && value >= -1.0 ? value * 100 : value;
  final numStr = formatNumber(fallbackPercentValue,
      locale: locale, decimalDigits: decimalDigits);

  if (['fr', 'de', 'ru', 'sv', 'pl', 'fi', 'no', 'cs'].contains(lang)) {
    return '$numStr %';
  }
  return '$numStr%';
}