test-coffeeShoppe.js

const coffeeShoppe = {};

coffeeShoppe.coffee = 5.25;
coffeeShoppe.latte = 4.25;
coffeeShoppe.cheesecake = 4.00;

/**
 * Get the price of the passed-in product name
 * @param  {string} productName
 * @return {number|undefined}
 */
coffeeShoppe.getPrice = function(productName) {
    return (typeof productName === 'string') ?
        this[productName] :
        undefined;
};

/**
 * Get the total price of a list of products
 * @param  {string[]} productList
 * @return {number}
 */
coffeeShoppe.calculateTotalPrice = function(productList) {
    let total = 0;

    if (!Array.isArray(productList)) {
        return total;
    }

    const productCount = productList.length;

    for (let i = 0; i < productCount; i++) {
        const price = this.getPrice(productList[i]);

        if (typeof price === 'number') {
            total += price;
        }
    }

    return total;
};

coffeeShoppe.calculateTotalPrice(['bagel', 'coffee', 'latte']);