Promise patterns

promises.md

Promise patterns in large JavaScript applications

• understand the abstraction
  • understand then (fmap/monadic bind)
• know the difference of deferred and promise
• be sure not to swallow errors
  • either return or end chain
  • error in success handler ending the chain
• resolve with a single value (jQuery...)
• standard error object for rejecting
• avoid async if not really needed
• always be fully async
  • add example
• promises compose nicely, use this to your advantage
  • write generic helpers
  • _.chain() <-> whenAllPromises
  • PromiseQueue
  • splitting tasks, sync duality with return statements
• parallellize all the IO you can
• be careful with imperative style and early returns