coffee-script loop efficiency

Question

super simple coffeescript question

circles = []
for coordinate, i in coordinates
    circles[i] = new MakeCircle(cnBlue, coordinate.x, coordinate.y, 16, 8, 0, theCanvas.ctx) 

This works. But I know that with the syntax candy there is probably and even more coffeescriptish way to write this. Is there a way to write this without using the i?

Answer 1

The canonical CoffeeScript way is to use a for comprehension, which will return an array:

circles = for coordinate in coordinates
  new MakeCircle(cnBlue, coordinate.x, coordinate.y, 16, 8, 0, theCanvas.ctx)

Or, on one line:

circles = (new MakeCircle(cnBlue, coordinate.x, coordinate.y, 16, 8, 0, theCanvas.ctx) for coordinate in coordinates)

See Loops and Comprehensions:

Note how because we are assigning the value of the comprehensions to a variable in the example above, CoffeeScript is collecting the result of each iteration into an array.