Promises in Coffeescript

1-promises.coffee

# Create a promise:

myCoolPromise = new Promise (resolve, reject) ->
  # do a thing
  success = true
  if success
    resolve 'stuff worked'
  else
    reject Error 'it broke'

# Use the promise:

myCoolPromise.then (result) ->
  console.log result # returns 'stuff worked'
.catch (error) ->
  console.log error # returns error: 'it broke'

2-promises-as-function.coffee

# You can also define a promise as a function:

myCoolPromise = () ->
  return new Promise (resolve, reject) ->
  # do a thing
  success = true
  if success
    resolve 'stuff worked'
  else
    reject Error 'it broke'

# Use the promise:

myCoolPromise(param).then (response) ->
  console.log 'success', response
.catch (error) ->
  console.error 'failed', error

3-promises-chaining.coffee

# You can also chain thens in a promise:
## (handy for running a bunch of async things in sequence)

myCoolPromise.then (result) ->
  console.log result # returns 'stuff worked'
  return 'abc'
.then (response) ->
  console.log response # returns 'abc'
.catch (error) ->
  console.error error
  asyncRecovery() # asyncRecovery error handler can have it's own promise chain 
.then ()
  console.log 'all done'

4-chaining-promises-together.coffee

Promise.all [myCoolPromise, myOtherCoolPromise].then (arrayOfResults)->
  # this part will run after all promises have finished
  console.log 'yay my promises finished'

there are fancier promise things you can do (see http://www.html5rocks.com/en/tutorials/es6/promises/) but the above will get you through 95% of life in a non scary way.

Thanks, it helps me 👍

appreciate the examples

for 2-promises-as-function.coffee should line 3 be this instead?: myCoolPromise = (param) ->

It's not clear to me how the param is used