Значение прототипа
String Number.0.97.8.582..6985849
90.864.2.3.4.1..5785.9.6..77
Clever Crab
String Number.0.97.8.582..6985849
90.864.2.3.4.1..5785.9.6..77String.prototype.countCharacter = function(char) {
return [...this].filter(c => c === char).length;
}