Multiple Line "If" Statement in CoffeeScript

Creating if statements that span multiple lines in CoffeeScript can be hard to remember, but it's quite easy. The trick is to make sure you

• keep your indentation the same, and
• end a line with an operator or a backslash

Simple Examples

Each of these examples will work, but they aren't necessarily pretty.

1. Backslash

Use a backslash to continue the line:

if a == 1 && b == 1 \
|| c == 1 && d == 1
  doSomething()

2. "Or" Operator

Use an "or" operator at the end of a line:

if a == 1 && b == 1 ||
c == 1 && d == 1
  doSomething()

3. Parentheses

Use parentheses (and an "or" operator):

if(
  a == 1 && b == 1 ||
  c == 1 && d == 1
)
  doSomething()

Refactoring

Let's do a bit of refactoring to see how we can make these a little cleaner.

1. Whitespace

Although it may seem odd, the indentation in CoffeeScript is looking for two spaces for it subsequent line. So if you use more than two, it will work as a continuation of the previous line. For example:

if a == 1 && b == 1 ||
   c == 1 && d == 1
  doSomething()

2. Parentheses

If that's hard to read, you can include parentheses.

if(a == 1 && b == 1 ||
   c == 1 && d == 1)
  doSomething()

3. Break Up Logic

Or, you could break up the logic into multiple statements.

e = a == 1 && b == 1
f = c == 1 && d == 1
if e && f
  doSomething()

Note: I prefer symbols for operators, such as && vs. and as I actually find it easier to read, even though it's less semantic. You can substitute my && for and and || for or and achieve the same effect.

References:

• CoffeeScript Issue #966