Ternary operation in CoffeeScript

Ternary operation in CoffeeScript

I need to set value to a that depends on a condition.
What is the shortest way to do this with CoffeeScript?
E.g. this is how I’d do it in JavaScript:
a = true ? 5 : 10 # => a = 5
a = false ? 5 : 10 # => a = 10

Solutions/Answers:

Solution 1:

Since everything is an expression, and thus results in a value, you can just use if/else.

a = if true then 5 else 10
a = if false then 5 else 10

You can see more about expression examples here.

Solution 2:

a = if true then 5 else 10
a = if false then 5 else 10 

See documentation.

Solution 3:

In almost any language this should work instead:

a = true  && 5 || 10
a = false && 5 || 10

Solution 4:

Coffeescript doesn’t support javascript ternary operator.
Here is the reason from the coffeescript author:

I love ternary operators just as much as the next guy (probably a bit
more, actually), but the syntax isn’t what makes them good — they’re
great because they can fit an if/else on a single line as an
expression.

Their syntax is just another bit of mystifying magic to memorize, with
no analogue to anything else in the language. The result being equal,
I’d much rather have if/elses always look the same (and always be
compiled into an expression).

So, in CoffeeScript, even multi-line ifs will compile into ternaries
when appropriate, as will if statements without an else clause:

if sunny   
  go_outside() 
else   
  read_a_book().

if sunny then go_outside() else read_a_book()

Both become ternaries, both can be used as expressions. It’s consistent, and there’s no new syntax to learn. So, thanks for the suggestion, but I’m closing this
ticket as “wontfix”.

Please refer to the github issue: https://github.com/jashkenas/coffeescript/issues/11#issuecomment-97802

Solution 5:

You may also write it in two statements if it mostly is true use:

a = 5
a = 10 if false

Or use a switch statement if you need more possibilities:

a = switch x
  when true then 5
  when false then 10

With a boolean it may be oversized but i find it very readable.

Solution 6:

Multiline version (e.g. if you need to add comment after each line):

a = if b # a depends on b
then 5   # b is true 
else 10  # b is false