var users = [{
  name: "Вася",
  surname: 'Иванов',
  age: 20
}, {
  name: "Петя",
  surname: 'Чапаев',
  age: 25
}, {
  name: "Маша",
  surname: 'Медведева',
  age: 18
}];

function byField(field) {
    return function(a, b) {
      return a[field] > b[field] ? 1 : -1;
    }
  }