Coffeescript equivalent of python 'pass' statement

Question

In Python one can use the 'pass' statement to do nothing:

if true:
    pass

Is there a similar statement in coffeescript? I'm trying to do a switch statement and do nothing if certain conditions are met.

switch variable:
  when 5 then pass
  else do variable

Answer 1

i'm a happy user of

switch x
  when 1
   null
  when 2
   y = 3
  else
   y = 4

since null is already in the language and does semantically transport that meaning of 'nothing'.

Answer 2

Unlike in Python, empty blocks are (usually) valid in CoffeeScript. So you can simply use:

switch variable:
  when 5 then
  else
    variable

Note that without the then it won't compile, which I find a bit odd. This works pretty generally, though:

if x
else if y
  something()
else
  somethingElse()

is perfectly valid CoffeeScript.

Answer 3

Because every expression has a value in CoffeeScript, a pass keyword, if it existed, would be equivalent to the value undefined. So, you could define

pass = undefined

and then use pass just like in Python:

switch variable
   when 5
     pass
   else
     do variable

Answer 4

I always use a semicolon for this:

switch variable
  when 5 then ;
  else do variable

This is because in javascript, a semicolon is a valid statement which also happens to do nothing.

Update: I just thought of another interesting way of doing this. You could define pass as a global variable and set it to undefined:

window.pass = undefined

switch variable
  when 5 then pass
  else do variable

The only thing you have to watch out for is using pass as a local variable or redefining the global pass variable. That would break your code.

If you use Google's closure compiler, you could annotate this variable so that it is a constant:

`/** @const */ var pass;`

But then it would have to go at the beginning of each file. You could write your own preprocessor to do that automatically, though.