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'

native promises work in node and all modern browsers (not IE11, but whatever)

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