In an if statement, is there any instance where the code would run for the "if" and the "else"?

(Please excuse the nested ifs, just learning this stuff as I go along)

Below is the code that's not working, the if and else, in the for/in loop, both run.

function checkCart(product) {
    if (cart.length == 0) {
        cart.push(product);
        addItemToCart(product);
    } else {
        for (let item in cart) {
            if (cart[item].productName == product.productName) {
                product.quantity += 1;
                updateCartQuantity(product);
            } else {
                cart.push(product);
                addItemToCart(product);
            }
        }
    }
}

Full code:

let cart = [];
let cartTotal = 0;
let cartAmountItems = 0;
let productsArr = [
    {
        productName: "Blender",
        productPrice: 1699,
        src: "./images/blender.jpg",
        quantity: 1,
    },
    {
        productName: "Xbox",
        productPrice: 9000,
        src: "./images/xbox.jpg",
        quantity: 1
    },
    {
        productName: "Chair",
        productPrice: 800,
        src: "./images/chair.jpg",
        quantity: 1
    },
    {
        productName: "Microwave",
        productPrice: 1800,
        src: "./images/microwave.jpg",
        quantity: 1
    },
    {
        productName: "Table",
        productPrice: 900,
        src: "./images/table.jpg",
        quantity: 1
    },
    {
        productName: "TV",
        productPrice: 18000,
        src: "./images/tv.jpg",
        quantity: 1
    },
]

let itemsDiv = document.querySelector("#items");

for (const product of productsArr) {
    itemsDiv.innerHTML += `
    <div class="productItem">
        <img src="${product.src}" class="productImage">
        <span class="productName">${product.productName}</span>
        <hr>
        <span class="productPrice">R${product.productPrice}</span>
        <button class="addToCart">Add to cart</button>
    </div>
    `
}

let addToCartBtn = document.getElementsByClassName("addToCart");
for (let x = 0; x < addToCartBtn.length; x++) {
    addToCartBtn[x].addEventListener('click', event => {
        let item = event.path[1].childNodes[3].innerHTML;
        for (const product of productsArr) {
            if (product.productName == item) {
                checkCart(product);
                addToTotal(product);
                addToCartAmount();
            }
        }
    });
}

function checkCart(product) {
    if (cart.length == 0) {
        cart.push(product);
        addItemToCart(product);
    } else {
        for (let item in cart) {
            if (cart[item].productName == product.productName) {
                product.quantity += 1;
                updateCartQuantity(product);
            } else {
                cart.push(product);
                addItemToCart(product);
            }
        }
    }
}

function updateQuantity(product) {
    for (let item in cart) {
        if (cart[item].productName == product.productName) {
            product.quantity += 1;
        }
    }
}

function addToTotal(product) {
    cartTotal += product.productPrice;
    document.getElementById('cartTotal').innerHTML = cartTotal;
}

function addToCartAmount() {
    cartAmountItems = cartAmountItems + 1
    document.getElementById('cartAmountItems').innerHTML = cartAmountItems;
}

function addItemToCart(product) {
    document.getElementById('cart').innerHTML +=
        `<div class="newItem">
            <img src="${product.src}" alt="${product.productName}">
            <p>${product.productName}</p>
            <p>R ${product.productPrice}</p>
            <p id="${product.productName}-Quantity">${product.quantity}</p>
        </div>`
}

function updateCartQuantity(product) {
    document.getElementById(`${product.productName}-Quantity`).innerHTML = product.quantity;
}

Thank you for any help.