find

Finds the first matching element.

find [ 1, 2, 3 ]
  def elt
    (elt % 2) == 0
# f.ret --> 2

With objects (maps), it returns the first matching entry (pair).

find { a: 'A', b: 'B', c: 'C' }
  def key, val
    val == 'B'
# f.ret --> [ 'b', 'B' ]

iterating and functions

Iterating functions accept 0 to 3 arguments when iterating over an array and 0 to 4 arguments when iterating over an object.

Those arguments are [ value, index, length ] for arrays. They are [ key, value, index, length ] for objects.

The corresponding key, val, idx and len variables are also set in the closure for the function call.