sample.js

for (let i = 0; i < people.length; i++) {
    console.group('person:' + people[i].name);
    console.group('pets');
    for (let j = 0; j < people[i].pets.length; j++) {
        console.log(people[i].pets[j]);
    }
    console.groupEnd();
    console.groupEnd();
}