Default values with object / array destructuring in CoffeeScript

destructuring-with-default-values.coffee

# You can have default values in object destructuring

o1 = a: 1, b: 2
{ a, b, c = 3} = o1
c is 3

o2 = a: 1, b: 2, c: 5
{ a, b, c = 3} = o2
c is 5

# Same with array:
a1 = [ 1, 2 ]
[ a, b, c = 3 ] = a1
c is 3

a2 = [ 1, 2, 5 ]
[ a, b, c = 3 ] = a2
c is 5

# Works really nice with options function parameters with destructuring in signature:
fn = ({a, b, c = 3}) -> c

(fn a: 1, b: 2) is 3

(fn a: 1, b: 2, c: 5) is 5