gistfile1.js

function Hamburger(size, filling, extra){
    size = size.toUpperCase();
    filling = filling.toUpperCase();
    extra = (extra!==null) ? extra.toUpperCase() : extra;
    
    this.CONSTANTS = {
        SMALL: {price: 50, calorie: 20},
        BIG: {price: 100, calorie: 40},
        CHEESE: {price: 10, calorie: 20},
        SALAD: {price: 20, calorie: 5},
        POTATOES: {price: 15, calorie: 10},
        SAUCE: {price: 20, calorie: 5},
        SPICE: {price: 15, calorie: 0}
    };
    
    this.size = size;
    this.filling = filling;
    this.extra = extra;
}

Hamburger.prototype.calculate = function(){
    try{
        if(this.extra!=null){
            var price = this.CONSTANTS[this.size].price + this.CONSTANTS[this.filling].price
                        + this.CONSTANTS[this.extra].price;
            var calorie = this.CONSTANTS[this.size].calorie
                          + this.CONSTANTS[this.filling].calorie
                          + this.CONSTANTS[this.extra].calorie;
        }else{
            var price = this.CONSTANTS[this.size].price + this.CONSTANTS[this.filling].price;
            var calorie = this.CONSTANTS[this.size].calorie + this.CONSTANTS[this.filling].calorie;
        }
        return {'price': price, 'calorie': calorie};
    }catch(e){
        console.log('Вы ввели неправильный тип гамбургера, начинки или добавки.');
    }
};

var hamburger = new Hamburger('big', 'salad', 'sauce');
console.log(hamburger.calculate());