Ternary operation in CoffeeScript

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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


answered 6 years ago loganfsmyth #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.

answered 6 years ago Paul Oliver #2

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

See documentation.

answered 5 years ago Alexander Senko #3

In almost any language this should work instead:

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

answered 3 years ago Alinex #4

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.

answered 1 year ago Max Peng #5

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   

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

answered 5 months ago Mikhail Khazov #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

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