A simple javascript to ordered the collection through given property and also calculate the average

sample.js

(function() {
  'use strict';
  
  // create a person
  function Person(name, ranking) {
    this.name = name;
    this.ranking = ranking;
    this.toString = function() {
      return '[' + this.name + ' ' + this.ranking + ']';
    }
  }
  
  // sort by given property
  Array.prototype.sortBy = function(prop) {
    return this.slice(0).sort(function(o1, o2) {
      if (o1[prop] > o2[prop]) {
        return 1;
      } else if (o1[prop] < o2[prop]) {
        return -1;
      }
      return 0;
    });
  };
  
  // calculate the average for given property i.e number
  Array.prototype.average = function(prop) {
    var average = 0;
    this.forEach(function(obj) {
      if (typeof obj[prop] === 'number') {
        average += obj[prop];
      }
    });
    return average;
  };
  
  // print the array
  Array.prototype.print = function() {
    return this.slice(0).toString();
  };
  
  // create the person object array
  var personItems = [
    new Person('John', 32), 
    new Person('Martin', 18),
    new Person('Steve', 26)
  ];
  
  // sort array w.r.t age and name
  var sortByName = personItems.sortBy('name');
  var sortByAge = personItems.sortBy('ranking');
  var average = personItems.average('ranking');
  
  // print the output on console
  console.log('SortBy Name: ', sortByName.print());
  console.log('SortBy Age: ', sortByAge.print());
  console.log('Average Ranking: ', average);
  
})();

Result:

SortBy Name:  [John 32],[Martin 18],[Steve 26]
SortBy Age:  [Martin 18],[Steve 26],[John 32]
Average Ranking:  76