Как установить рендер для rowexpander в ext.net или extjs?

Немного устарел, но вот функция, которую вы можете использовать!

function calculateAge(birthMonth, birthDay, birthYear) {
    var currentDate = new Date();
    var currentYear = currentDate.getFullYear();
    var currentMonth = currentDate.getMonth();
    var currentDay = currentDate.getDate(); 
    var calculatedAge = currentYear - birthYear;

    if (currentMonth < birthMonth - 1) {
        calculatedAge--;
    }
    if (birthMonth - 1 == currentMonth && currentDay < birthDay) {
        calculatedAge--;
    }
    return calculatedAge;
}

var age = calculateAge(12, 8, 1993);
alert(age);