Control Structures

Related: Comprehensions and Iteration

Single Test: if and unless

if foo then bar
if foo then bar else baz
if foo
  bar
else
  baz

unless foo then bar else baz
# if !foo then bar else baz

Return Values

If and Unless return the value returned by their blocks. If there is no else-block and the test is false-for-if or true-for-unless, then undefined is returned.

Multi-Test: switch

switch a
when b then c
when d
  e
else
  f

switch a
  when b then c
  else d

NOTE: unlike coffeescript, indentation is optional.

Multi-Test Form

As an alternative to if-then-else chains, you can use the switch statement this way:

switch
when testA then doA
when testB then doB
else elseC

# same as
if testA then doA
else if testB then doB
else elseC

Where testA and testB are arbitrary expressions.

Return Values

Switch statements return-values work just like if-statements: If one of the switch's cases is selected, the return-value of that case's then-block is returned. If no cases are found, and there is an else-block, the else-block's return-value is returned. Finally, if no cases are found and there is no else-block, undefined is returned.

Basic Loops: while and until

These give you direct access to JavaScript's basic looping construct: while.

COMING SOON: These blocks will define scopes, just like the Caffeine-Specific Comprehensions and Iteration. See also: Scopes and Variables.

while foo do bar
while foo
  bar

unless foo do bar
# while !foo do bar

Return Values

While and Until return the last value returned by their block. (coming soon)

Disambiguation with Block Invocation

if foo
    1
  2
# if foo(1) then 2

Tail Forms: if, unless, while, and until

There are four tail-forms available for enhanced code readability:

foo if bar     # if bar then foo
foo unless bar # if !bar then foo
foo while bar  # while bar do foo
foo until bar  # while !bar do foo