JSFiddle - React, Tailwind, and code Playground

JavaScript

function sortq(array, num){
    var arResult = [];

    arResult = array.sort(function (a, b) {
          if (a.population > b.population) {
            return 1;
          }
          if (a.population < b.population) {
            return -1;
          }
          return 0;
        });

    return arResult.slice(0, num);
}
console.log(sortq(cities, 3));