sortByAge.js

var persons = [
  { name: 'Jhon', age: 21 },
  { name: 'Alice', age: 37 },
  { name: 'Brenda', age: 45 },
  { name: 'Manuel', age: 12 },
  { name: 'Maria', age: 37 }
];

function sortByAge(persons) {
    return persons.sort(function(a, b){
        return a.age - b.age;
    });
}