Promise is better value


Promise is more than a value

A Promise is a wrapped “async result of computation”.

It may throw a error or never ends.

always async

  • Handlers (then / catch) are guaranteed to be called async
    • As of Promise/A+ spec, there is no interface to examine result in a sync way (exists in libraries like Bluebird though)
  • Order of execution are expressed via dependicies, just as in plain sync code