Can't figure out a portion of JavaScript code. Any suggestions?

var hyveeList = {};
var coopList = {};
var results = '';

//some data to work with
var foods = [
    ['hyvee', 'bread', 'fresh', 2.00],
    ['hyvee', 'peanut butter', 'fresh', 3.00],
    ['hyvee', 'jelly', 'fresh', 2.50],
    ['hyvee', 'apple juice', 'fresh', 5.00],
    ['coop', 'bread', 'fresh', 2.50],
    ['coop', 'peanut butter', 'fresh', 3.50],
    ['coop', 'jelly', 'fresh', 2.50],
    ['coop', 'apple juice', 'fresh', 4.75]
];

//your original function
function input(location, food, freshness, price) {
    if(location.toLowerCase() === "hyvee") {
        hyveeList[food] = {location: location, freshness: freshness, price: price};
    } else if(location.toLowerCase() === "coop") {
        coopList[food] = {location: location, freshness: freshness, price: price};
    } else {
        console.log("The location you selected is not a part of this program");
    }
}

//loop through the data and send it to your function
function makeLists(foodArray){
    for(var i = 0, l = foodArray.length; i < l; i++){
        input(foodArray[i][0], foodArray[i][1], foodArray[i][2], foodArray[i][3]);
        //can also do the following way if you undertsand what's going on:
        //window.input.apply(window, foodArray[i]);
    }
}

//compare foods in the lists
function compareLists(list1, list2){
    //if you return in a loop it will stop the loop, 
    //so push the value into an array and return the array when loop is done
    var listResults = [];

    //loop through list 1 (assumes both lists contains same food)
    for(var food in list1){
        //verify food also exists in list 2
        if(list2[food]){
            if(list1[food].price > list2[food].price){
                //list 1 is more expensive. Get price to 2 decimal points
                listResults.push( list2[food].location + ' ' + food +' is cheaper by $' + (list1[food].price - list2[food].price).toFixed(2));
            }else if(list1[food].price < list2[food].price){
                //list 2 is more expensive. Get price to 2 decimal points
                listResults.push( list1[food].location + ' ' + food +' is cheaper by $' + (list2[food].price - list1[food].price).toFixed(2));
            }else{
                //same price in both lists
                listResults.push('At both stores ' + food + ' is the same price');
            }
        }
    }

    //returns array of values
    return listResults;
}

//Do the work
makeLists(foods);
results = compareLists(hyveeList, coopList);
console.log(results.join(', '));