JSFiddle - React, Tailwind, and code Playground

JavaScript

var people = [{
  "fname": "shiva",
  "lname": "kiran",
  "age": 20
}, {
  "fname": "aru",
  "lname": "wind",
  "age": 21
}, {
  "fname": "shiva",
  "lname": "charan",
  "age": 19
}];

var compare = function(a, b) {
  var ret = a.fname.localeCompare(b.fname)
  if (ret === 0) {
    return b.age - a.age;
  }
  return -1 * ret;
};

people.sort(compare);
console.log(people);