Untitled

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>

<div>
    <ul>
        <li>
            <span class="product-name">Product 1</span>
            <input type="text" class="qty-input" id="qty-1">
        </li>
        <li>
            <span class="product-name">Product 2</span>
            <input type="text" class="qty-input" id="qty-2">
        </li>
        <li>
            <span class="product-name">Product 3</span>
            <input type="text" class="qty-input" id="qty-3">
        </li>
    </ul>
    <button type="submit" id="submit">Buy</button>
</div>

<script type="text/javascript">
$(document).ready(function(){
  // event on click
  $("#submit").click(function(){
    // loop
    $(".qty-input").each(function() {
        var productName = $(this).siblings('.product-name').text();

        if ($(this).val()) {
            alert('Product: ' + productName + '; Qty: ' + $(this).val());
        }
    });
  });
});
</script>

</body>
</html>