function checkPrice(products, productsPrices, productsSold, soldPrice){
    let hash = {};
    let count = 0;

    // iterate over products and map price 
    // {"eggs":2.89, "milk": 2.29, "cheese": 5.79}
    for(let i=0; i < products.length; i++){
        // check if hash object has already product key available
        // if it is not present 
        // assign a key and it's value from productsPrices
        if(!hash[products[i]]){
            hash[products[i]] = productsPrices[i]
        }
    }

    // iterate over products/productsSold
    // check for alreday stored price in hash
    // if it is mismatching 
    // increase the count to show errors count
    for(let j=0; j < productsSold.length; j++){
        if(hash[productsSold[j]] !== soldPrice[j]){
            count++;
        }
    }

    return count;
}


let products = ["eggs", "milk", "cheese"];
let productsPrices = [2.89, 3.29, 5.79];
let productsSold = ["eggs", "eggs", "cheese", "milk"];
let soldPrice = [2.89, 2.99, 5.97, 2.39];

checkPrice(products, productsPrices, productsSold, soldPrice);