Example showcasing reduce function

reduceExample.js

// For the data set given below, find room which is false for all suspects (objects in the newDevelopment array)
const newDevelopment = [
    {
        name: 'Miss Scarlet',
        present: true,
        rooms: [
            {kitchen: false},
            {ballroom: false},
            {conservatory: true},
            {'dining room': true},
            {'billiard room': false},
            {library: true}
        ]
    },
    {
        name: 'Reverend Green',
        present: true,
        rooms: [
            {kitchen: true},
            {ballroom: false},
            {conservatory: false},
            {'dining room': false},
            {'billiard room': true},
            {library: false}
        ]
    },
    {
        name: 'Colonel Mustard',
        present: true,
        rooms: [
            {kitchen: false},
            {ballroom: false},
            {conservatory: true},
            {'dining room': false},
            {'billiard room': true},
            {library: false}
        ]
    },
    {
        name: 'Professor Plum',
        present: true,
        rooms: [
            {kitchen: true},
            {ballroom: false},
            {conservatory: false},
            {'dining room': true},
            {'billiard room': false},
            {library: false}
        ]
    }
];

function intersection(rooms1, rooms2) {
    const intersection = [];
    rooms1.forEach(room => {
        if (rooms2.includes(room)) {
            intersection.push(room);
        }
    });
    return intersection;
}

const listOfListOfRooms = [];
newDevelopment.forEach(suspect => {
    const listOfRooms = suspect.rooms
        .filter(room => Object.values(room).includes(false))
        .flatMap(room => Object.keys(room));
    listOfListOfRooms.push(listOfRooms);
});

console.log(listOfListOfRooms.reduce(intersection));