after-actions.ts

// after actions on client side

webln.sendPayment(invoice, metadata)
  .then(function (r) {
    // Required constraint to protect metadata as a rule while paying empty invoices
    if (r != undefined) {
      // Provide metadata after successful payment
      // Eg. Allow users to download a song after payment is successful
    }
  })
  .catch(function (e) {
    alert("Failed: " + e.message);
    console.log('err pay:', e);
   });