How to : click button to open shopping basket available in another html file

I have an index.html with navigation bar, another html file for shopping basket and basket.js/ basket.css files. When you click on button basket in index.html you show the Basket.html file.how can i make it work?

I tried the following:

index.html:

<head>
    <meta charset="UTF-8">
    <link rel="stylesheet" href="css/basket.css">
    <title>Product List</title>
</head>
<body>
<div class="navbar" style="overflow:hidden; background-color:#009650; position:fixed; top:0; width:100%;" >
    <button id="basket-button" onclick="window.location.href='/Basket.html'"> Basket </button>
<script src="js/Basket.js"></script>
</body>

Basket.html:

<head>
    <meta charset="UTF-8">
    <link rel="stylesheet" href="css/basket.css">
    <title>Basket</title>
</head>
<div class="basket" id="shopping-basket">
    <div class="item">
        <div class="buttons">
            <span class="delete-btn"></span>
            <span class="like-btn"></span>
        </div>

        <div class="image">
        
        </div>

        <div class="description">
            <span>product name</span>
        </div>
        <div class="quantity">
            <button class="plus-btn" type="button" name="button">
            </button>
            <input type="text" name="name" value="1">
            <button class="minus-btn" type="button" name="button">
            </button>
        </div>
        <div class="total-price"></div>
<script src="js/Basket.js"></script>

Basket.js:


window.onload = () => {
  document.getElementById("basket-button").onclick = function() {myFunction()};
  function myFunction() {
    document.getElementById("shopping-basket").classList.toggle("show");
  }
}

basket.css:


   .basket{ display: none;}
   .basket.show {display:block;
                 position: absolute;
                 left:80%;
                 margin-top: 30px;
                 padding: 5px;
                background-color: #43484D;}

   .basket.hide {
      display:none;
    }