Getting console errors while setting up client to call server side PayPal API

While setting up, PayPal client code to test server integration, from https://developer.paypal.com/docs/archive/checkout/how-to/server-integration/

My code is as follows:

<html>
<head>
    <title>TEST PAYMENT</title>
</head>
<body>    
<div id="paypal-button"></div>
<script src="https://www.paypalobjects.com/api/checkout.js"></script>
<script>
  paypal.Button.render({
    env: 'sandbox', // Or 'production'
    
    // Set up the payment:
    // 1. Add a payment callback
    payment: function(data, actions) {
      // 2. Make a request to your server
      return actions.request.post('/api/paypal/create-payment')
        .then(function(res) {
            console.log(res);
          // 3. Return res.id from the response
          return res.id;
        });
    },

    // Execute the payment:
    // 1. Add an onAuthorize callback
    onAuthorize: function(data, actions) {
      // 2. Make a request to your server
      return actions.request.post('/api/paypal/execute-payment', {
        paymentID: data.paymentID,
        payerID:   data.payerID
      })
        .then(function(res) {
          // 3. Show the buyer a confirmation message.
        });
    }
  }, '#paypal-button');
</script>
</body>
</html>

When I open the page.

When I click the button, a modal window shows up for a second and closed with the following errors.

Solution

The checkout.js integration you're attempting to use is deprecated.

Here is the current JS SDK to call your server with: https://developer.paypal.com/demo/checkout/#/pattern/server