Don’t ignore rejected promises

For the same reason you shouldn’t ignore caught errors from try/catch.

Bad:

getdata()
  .then(data => {
    functionThatMightThrow(data);
  })
  .catch(error => {
    console.log(error);
  });

Good:

getdata()
  .then(data => {
    functionThatMightThrow(data);
  })
  .catch(error => {
    // One option (more noisy than console.log):
    console.error(error);
    // Another option:
    notifyUserOfError(error);
    // Another option:
    reportErrorToService(error);
    // OR do all three!
  });