01-PlanarSystem | 02-CustomRemove | 03-DeepCopy | 04-PropChecker | 05-YoungestPerson | 06-Grouping

// 06. Write a function that groups an array of persons by age, first or last name. The function must return an associative array,
with keys - the groups, and values -arrays with persons in this groups
Use function overloading (i.e. just one function)
var persons = {…};
var groupedByFname = group(persons,"firstname");
var groupedByAge= group(persons,"age");