the lift - fundamentals

function theLift(arr) {
    let people = Number(arr[0]);
    let wagons = arr[1].split(" ").map(Number);

    //пълним вагоните -> max 4:

    while (people !== 0 || isFree(wagons)) {

        wagons = wagons.map(w => {  //0 2 0 => 4 2 0 => 4 4 0
            let n = 4 - w;
            if (n > people) {
                n = people;
            }
            people -= n;
            w += n;
            return w;
        });

    }
    if (isFree(wagons)) {
        console.log(`The lift has empty spots!`);
    }
    if (people > 0) {
        console.log(`There isn't enough space! ${people} people in a queue!`);
    }
    console.log(wagons.join(" "));

    function isFree(array) {
        let filtered = array.filter(x => x < 4);
        return filtered.length > 0;
    }
}