coffeescript chaining with no parameters?

Question

Hi I'm wondering if its possible to omit empty parenthesis when chaining in coffeescript.

for example

myFunction = -> [...]
chain1     = -> [...]
chain2     = -> [...]  
myFunction().chain1().chain2()

to instead

myFunction.chain1.chain2

Answer 1

Short answer: no, you can't.

That exact syntax will not work in CoffeeScript. You can only chain methods that have at least one argument, so something like this could work:

myFunction arg1
  .chain1 arg2
  .chain2 arg3

For jQuery, for example, you can do stuff like:

$ ->
  $ '#foo'
    .and '.bar'
    .click ->
      alert 'awesome!'

This is because, unlike in Ruby, where referencing a name without a leading '@' or '::' implies a method or a local variable, in CoffeeScript, myFunction is an expression that returns the function itself. Thus, myFunction.chain1 and myFunction().chain1 can both be valid and mean different things.

Note however, that the new keyword implies a function call, so if myFunction is an (oddly named) constructor, you could write (new myFunction).chain1, but that is again different as .chain1 would be the property of the prototype.

Moreover, if you are the author of the library in question, you could use getters/setters to simulate that behaviour in plain JavaScript, but I would highly discourage that.