if(window.PaymentRequest) {
  // Use Payment Request API
  // Checkout details
                var details = {
                    displayItems: [{
                        label: 'Tax Cost',
                        amount: { currency: 'GBP', value: '77.00' }
                    }, {
                        label: 'Early payment discount',
                        amount: { currency: 'GBP', value: '-15.00' }
                    }],
                    total: {
                        label: 'Total due',
                        amount: { currency: 'GBP', value: '62.00' }
                    }
                };
} else {
  // Fallback to traditional checkout
  window.location.href = '/checkout/traditional';
}