// array of objects
var arrayOfObjects = [
  {
    name: "Stannis Baratheon",
    rank: 2
  },
  {
    name: "Eddard Stark",
    rank: 1
  },
  {
    name: "Brandyn Tully",
    rank: 4
  },
  {
    name: "Davos Seaworth",
    rank: 3
  },
  {
    name: "Bronn",
    rank: 5
  },
  {
    name: "Jaqen H'ghar",
    rank: 8
  },
  {
    name: "Beric Dondarrian",
    rank: 6
  },
  {
    name: "Sandor Clegane",
    rank: 9
  },
  {
    name: "Thoros of Myr",
    rank: 7
  },
  {
    name: "Oberyn Martell",
    rank: 11
  },
  {
    name: "Barriston Selmy",
    rank: 10
  }
];

// make a copy of array of object
var copyOfArray = arrayOfObjects.slice(0); // with slice we make a copy not refrence

// function to sort the array of object by rank
const funcToSortByRank = copyOfArray => {
  copyOfArray.sort((a, b) => {
    return a.rank - b.rank;
  });
  console.log(copyOfArray);
};

// function to find average rank
const funcForFindAvg = (array, key) => {
  let average = array.reduce(function(r, a) {
    return r + a[key];
  }, 0);
  console.log("Average rank :" + average / array.length);
};

// function calls
funcToSortByRank(copyOfArray);
funcForFindAvg(copyOfArray, "rank");