payment.js

function onBuy() {
  // Define supported credit card
  var supportedInstruments = [{
    supportedMethods: ['amex', 'diners', 'discover', 'jcb', 'mastercard',
        'unionpay', 'visa']
  }];
  //Order detail
  var details = {
    total: {label: 'Product', amount: {currency: 'THB', value: '10.00'}},
    displayItems: [
      {
        label: 'Product Item #1',
        amount: {currency: 'THB', value: '10.00'}
      }
    ]
  };
  // Make payment Request
  new PaymentRequest(supportedInstruments, details) // eslint-disable-line no-undef
      .show()
      .then(function(instrumentResponse) {
        sendPaymentToServer(instrumentResponse);
      })
      .catch(function(err) {
        console.log(err)
      });
}

function sendPaymentToServer(instrumentResponse) {
  // Implement sent data to Server here
    instrumentResponse.complete('success')
        .then(function() {
          console.log(instrumentResponse)
        })
        .catch(function(err) {
          console.log(err);
    });
}