Array.prototype.map shim for non-compliant browsers. Converted from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map.

map.coffee

# Production steps of ECMA-262, Edition 5, 15.4.4.19
# Reference: http://es5.github.com/#x15.4.4.19
# from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map
unless Array::map
  Array::map = (callback, thisArg) ->
    T = undefined
    A = undefined
    k = undefined
    throw new TypeError(" this is null or not defined")  unless this?

    # 1. Let O be the result of calling ToObject passing the |this| value as the argument.
    O = Object(this)

    # 2. Let lenValue be the result of calling the Get internal method of O with the argument "length".
    # 3. Let len be ToUint32(lenValue).
    len = O.length >>> 0

    # 4. If IsCallable(callback) is false, throw a TypeError exception.
    # See: http://es5.github.com/#x9.11
    throw new TypeError(callback + " is not a function")  if typeof callback isnt "function"

    # 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
    T = thisArg  if thisArg

    # 6. Let A be a new array created as if by the expression new Array(len) where Array is
    # the standard built-in constructor with that name and len is the value of len.
    A = new Array(len)

    # 7. Let k be 0
    k = 0

    # 8. Repeat, while k < len
    while k < len
      kValue = undefined
      mappedValue = undefined

      # a. Let Pk be ToString(k).
      #   This is implicit for LHS operands of the in operator
      # b. Let kPresent be the result of calling the HasProperty internal method of O with argument Pk.
      #   This step can be combined with c
      # c. If kPresent is true, then
      if k of O

        # i. Let kValue be the result of calling the Get internal method of O with argument Pk.
        kValue = O[k]

        # ii. Let mappedValue be the result of calling the Call internal method of callback
        # with T as the this value and argument list containing kValue, k, and O.
        mappedValue = callback.call(T, kValue, k, O)

        # iii. Call the DefineOwnProperty internal method of A with arguments
        # Pk, Property Descriptor {Value: mappedValue, : true, Enumerable: true, Configurable: true},
        # and false.

        # In browsers that support Object.defineProperty, use the following:
        # Object.defineProperty(A, Pk, { value: mappedValue, writable: true, enumerable: true, configurable: true });

        # For best browser support, use the following:
        A[k] = mappedValue

      # d. Increase k by 1.
      k++

    # 9. return A
    A