свойство length
override
Количество пар «ключ/значение» в карте.
Реализация
int get length => JS('int', '#.size', this);
© 2012 the Dart project authors
Licensed under the BSD 3-Clause "New" or "Revised" License.
https://api.dart.dev/stable/2.19.6/dart-html/MidiInputMap/length.html
