Sort Array by Multiple Criteria

SortByMultipleCriteria.js

// Factory Function to combine multiple sort criteria
// receives functions representing sorting criteria
// returns a new function that applies these criteria 
function sortByMultipleCriteriaFactory(...sortFuncs){
    return (it1, it2) => {
        for (sort of sortFuncs){
            let res = sort(it1, it2);
            if (res !== 0){
                //for this criteria items are not equal (in sorting terms) so no more criteria to apply
				return res;
            }
        }
        return res;
    };
}

let sortByPopulation = (it1, it2) => {
    return (it1.population > it2.population)
    ? -1
    : (it1.population < it2.population)
    ? 1
    : 0;
};

let sortByName = (it1, it2) => {
    return (it1.name > it2.name)
    ? -1
    : (it1.name < it2.name)
    ? 1
    : 0;
};


let cities = [
    {
        name: "Palermo",
        population: 500000
    },
    {
        name: "Paris",
        population: 12000000
    },
    {
        name: "Bilbao",
        population: 500000
    },
    {
        name: "Xixon",
        population: 270000
    },
    {
        name: "Toulouse",
        population: 500000
    },
    {
        name: "Bologne",
        population: 500000
    }
];

let sortByPopulationAndName = sortByMultipleCriteriaFactory(sortByPopulation, sortByName);

console.log("before: " + cities.map(city => city.name).join("\n"));
cities.sort(sortByPopulationAndName);
console.log("after: " + cities.map(city => city.name).join("\n"));