Christmas Gifts

function christmasGifts(input) {
    let adults = 0;
    let kids = 0;

    for (let i = 0; i < input.length; i++) {
        let command = input[i];
        if (command === "Christmas") {
            break;
        }
        let years = Number(command);
        if (years <= 16) {
            kids++;
        } else {
            adults++;
        }
    }

    let kidsPrice = kids * 5;
    let adultsPrice = adults * 15;

    console.log(`Number of adults: ${adults}`);
    console.log(`Number of kids: ${kids}`);
    console.log(`Money for toys: ${kidsPrice}`);
    console.log(`Money for sweaters: ${adultsPrice}`);
}

РЕШЕНИЯ С WHILE:

function christmasGifts(input) {
    let command = input[0];
    let index = 1;
    let adults = 0;
    let kids = 0;

    while (command !== "Christmas") {
        let years = Number(command);
        if (years <= 16) {
            kids++;
        } else {
            adults++;
        }
        command = input[index++];
    }

    let kidsPrice = kids * 5;
    let adultsPrice = adults * 15;

    console.log(`Number of adults: ${adults}`);
    console.log(`Number of kids: ${kids}`);
    console.log(`Money for toys: ${kidsPrice}`);
    console.log(`Money for sweaters: ${adultsPrice}`);
}

Решение с тернарен оператор и леко тарикатската:)

function christmasGifts(input) {
    let command;
    let adults = 0;
    let kids = 0;

    while ((command = input.shift()) !== "Christmas") {
        Number(command) <= 16 ? kids++ : adults++;
    }

    console.log(`Number of adults: ${adults}\nNumber of kids: ${kids}\nMoney for toys: ${kids * 5}\nMoney for sweaters: ${adults * 15}`);
}