【Dart】数字格式化成 ‘...k'

  /// https://stackoverflow.com/a/9462382
  nFormatter(dynamic num, [int digits]) {
    var si = [
      {'value': 1, 'symbol': ''},
      {'value': 1e3, 'symbol': 'k'},
      {'value': 1e6, 'symbol': 'M'},
      {'value': 1e9, 'symbol': 'G'},
      {'value': 1e12, 'symbol': 'T'},
      {'value': 1e15, 'symbol': 'P'},
      {'value': 1e18, 'symbol': 'E'},
    ];
    var rx = RegExp(r'\.0+$|(\.[0-9]*[1-9])0+$');
    var i;
    for (i = si.length - 1; i > 0; i--) {
      if (num.abs() >= si[i]['value']) {
        break;
      }
    }
    return (num / si[i]['value']).toStringAsFixed(digits).replaceAll(rx, '') +
        si[i]['symbol'];
  }
}