Please save your file with .php extension.  You can assign php value into js variable and pass it to PayPal. I have attached sample code below: I am passing amount value from php variable.`<script>
  var total_price= '<?php echo $total_price; ?>';
   paypal.Buttons({
    createOrder: function(data, actions) {
      return actions.order.create({
        purchase_units: [{
          amount: {
            value: total_price
          }
        }]
      });//insert JSON above this line
    },
    onApprove: function(data, actions) {
      return actions.order.capture().then(function(details) {
        alert('Transaction completed by ' + details.payer.name.given_name);
        // Call your server to save the transaction
        return fetch('/BurgerJoint/GetOrder.php', {
          method: 'post',
          headers: {
            'content-type': 'application/json'
          },
          body: JSON.stringify({
            orderID: data.orderID
          })
        });
      });
    }
  }).render('#paypal-button-container');
  </script>`