Best way to handle early returns in chains of promises?

问题

What's the best way to handle early returns in Bluebird without throwing an error. For example, I have a conditional in the following:

things.find(1)
  .then(function(thing) {
    if (thing.condition === true) {
      return thing
    } else {
      // early return?
    }
  })
  .then(function(thing) {
    return doStuff(thing)
  })

回答1:

Once a .then chain is formed, its natural behaviour is to run progressively to completion as each of its stages settles.

For an "early return" (not a good phrase but we know what you mean), you have three options :

• throw an error, or return a rejected promise, to bypass all success handlers until the next catch (or the end of the chain)
• return a promise that is guaranteed never to settle - eg return new Promise()
• compose the .then chain responsively (Esailija's answer)

回答2:

things.find(1).then(function(thing) {
  if (!thing.condition) return;
  return doStuff(thing)
    .then(...);
    .then(...);
})

来源：https://stackoverflow.com/questions/29525354/best-way-to-handle-early-returns-in-chains-of-promises