Coffeescript shortcut for truthyness

Question

I often want to check if a variable or property is not null and not undefined in CS. Is there a shortcut for "truthy"-checks besides the postfix ? for undefined?

Answer 1

@Austin Mullins, Thats true but I assumed it produced that check for everything and found that the CoffeeScript compiler will produce different results based on the use of the variables.

Variables that are declared before use (assigned a value) check for != null. Even explicit assignment of undefined (the Javascript compiles to void 0 which returns undefined) won't change the compilers behaviour.

The result is the same regardless ? appears work as expected.

A demo of what I found (preview link), http://preview.tinyurl.com/cmo6xw7

Follow the link and click the Run button (top right)

The code...

((arg) ->
    str = "Hello World!"
    num = 42
    foo = arg

    # Lets see what the compiler produces  
    alert "str is #{str}" if str?
    alert "num is #{num}" if num?
    alert "foo is #{foo}" if foo?
    # bar has not been assigned a value or used until now
    alert "bar is #{bar}" if bar?

    # Lets assign str to something that isn't straight up null
    # cs will translate undefined into the expression that returns undefined
    str = undefined

    # Shorthand
    if str?
        alert "str? is #{str}"
    else
        alert "str? is empty"

    # Explicit checks
    if typeof str isnt "undefined" && str isnt null
        alert "str explicit check is #{str}"
    else
        alert "str explicit check is empty"

 ).call()