const test = [ { nation: { name: "Germany", iso: "DE", rankingPoints: 293949 } }, { nation: { name: "Hungary", iso: "HU", rankingPoints: 564161 } }, { nation: { name: "Serbia", iso: "SR", rankingPoints: 231651 } } ]; const sorted = test.sort((a, b) => a.nation.rankingPoints - b.nation.rankingPoints); // Using forEach: var dict = {} sorted.forEach((el, index) => dict[el.nation.iso] = sorted.length - index); // Using reduce: dict = sorted.reduce( (dict, el, index) => (dict[el.nation.iso] = sorted.length - index, dict), {} ); console.log(dict) console.log("dict['DE'] = ", dict['DE'])