Coffeescript deep object clone

clone.coffee

clone = (obj) ->
    return obj if not obj? or typeof obj isnt 'object'

    return new Date(obj.getTime()) if obj instanceof Date

    if obj instanceof RegExp
        flags = ''
        flags += 'g' if obj.global?
        flags += 'i' if obj.ignoreCase?
        flags += 'm' if obj.multiline?
        flags += 'y' if obj.sticky?
        return new RegExp(obj.source, flags)

    newInstance      = new obj.constructor()
    newInstance[key] = clone(obj[key]) for key of obj

    return newInstance