03.Store provision

function store (stockArr, orderArr) {
    let stockObj = {};

    for (let i = 0; i < stockArr.length; i+=2) {
        stockObj[stockArr[i]] = Number(stockArr[i + 1]);
    }

    for (let i = 0; i < orderArr.length; i+=2) {
        if (orderArr[i] in stockObj) {
            stockObj[orderArr[i]] += Number(orderArr[i + 1]);
        } else {
            stockObj[orderArr[i]] = Number(orderArr[i + 1]);
        }
    }

    for (let product of Object.keys(stockObj)) {
        console.log(`${product} -> ${stockObj[product]}`);
    }
}