Zero-based index. push mutates. slice does not.

Goal

Log cities and a pushed Eldoret.

const cities = ["Nairobi", "Mombasa", "Kisumu"];
console.log(cities[0]);
console.log(cities.length);

const cities = ["Nairobi", "Mombasa"];
cities.push("Kisumu");
console.log(cities);

const cities = ["Nairobi", "Mombasa", "Kisumu", "Nakuru"];
console.log(cities.slice(0, 2));
console.log(cities.includes("Eldoret"));

const units = [12, 8, 5];
console.log(units.join(", "));