CoffeeScript object creating helper

create.coffee

# A tiny helper for creating objects with dynamic keys. I found myself repeating the following pattern all over my code:

doStuff = ->
  obj = {}
  obj[k] = foo for k in bar()
  obj

# Which is not very elegant, and in many cases forces me to expand one-line functions into multiple lines.

# Instead, its possible to move the repeated pattern into a separate function:
create =  (fn) -> obj = {}; fn.call obj, obj; obj

# Than, we can do
doStuff = -> create -> @[k]=foo for k in bar()

# Or, if you need to preserve the `this` context and can't use `@`:
doStuff = -> create (o) => o[k] = foo for k in @bar()

Do note that the for loop inside the anonymous function generates a return value (as do all expressions in CoffeeScript), so you might want to use an empty return statement after the object creation to avoid creating an array with the results for each iteration (compare this to that).

Actually, coming to think about that - assuming you don't need the preserve the external this context and don't mind always adding am empty return (which you should do anyway), simply using new can work just as well:

doStuff = -> new -> @[k] = 123 for k in ['a','b','c'];return