Storing state at the top-level scope to be shared between promise handlers.

chain-promises.js

var user;
var balance;

getCurrentUser()
.then(function (currentUser) {
  user = currentUser;
  return getBalance(user);
})
.then(function (userBalance) {
  balance = userBalance;
  return deposit(user, 123);
})
.then(function (newBalance) {
  console.log("Deposit for user " + user.name + " old balance: " + balance + " new balance: " + newBalance);
});