Question

I have an object (an “associate array” so to say – also known as a plain JavaScript object):

obj = {}
obj["Foo"] = "Bar"
obj["bar"] = "Foo"

I want to iterate over obj using CoffeeScript as follows:

# CS
for elem in obj

bu the CS code above compiles to JS:

// JS
for (i = 0, len = obj.length; i < len; i++)

which isn’t appropriate in this case.

---

The JavaScript way would be for(var key in obj) but now I’m wondering: how can I do this in CoffeeScript?

Answer 1

Use for x,y of L. Relevant documentation.

ages = {}
ages["jim"] = 12
ages["john"] = 7

for k,v of ages
  console.log k + " is " + v

Outputs

jim is 12
john is 7

You may also want to consider the variant for own k,v of ages as mentioned by Aaron Dufour in the comments. This adds a check to exclude properties inherited from the prototype, which is probably not an issue in this example but may be if you are building on top of other stuff.