delay.ls

Q = require \q
p = [1 2 3]
q = [4 5 6]
(.reduce Q.when, Q!) <| for let i in p => ->
  <- Q.delay 500ms .then
  console.log i
  (.reduce Q.when, Q!) <| for let j in q => ->
    <- Q.delay 500ms .then
    console.log i, j

Flattened with helper:

Q = require \q
p = [1 2 3]
q = [4 5 6]
Q.map = (xs, f) -> xs.map((x) -> -> f x).reduce Q.when, Q!
i <- Q.map p
<- Q.delay 500ms .then
console.log i
j <- Q.map q
<- Q.delay 500ms .then
console.log i, j

{delay}:Q = require \q
p = [1 2 3]
q = [4 5 6]
each = (xs, f) -> xs.map((x) -> -> f x).reduce Q.when, Q!
each p, (i) ->
  console.log i
  <- delay 500ms .then
  each q, (j) ->
    console.log i, j
    <- delay 500ms .then