Better typeof

gistfile1.coffee

  toString = Object::toString
  hasOwnProperty = Object::hasOwnProperty
  propertyIsEnumerable = Object::propertyIsEnumerable
  ### @return `undefined|null|boolean|string|symbol|number|NaN|array|arguments|date|object|function` ###
  (val) ->
    switch type = typeof val
      when 'undefined', 'string', 'boolean', 'symbol'
        return type
      when 'number'
        return (if Number.isNaN(val) || (val in [Number.POSITIVE_INFINITY, Number.NEGATIVE_INFINITY]) then 'NaN' else type)
      when 'object', 'function'
        return if val == null
            'null'
          else if type == "object" && hasOwnProperty.call(val, 'length') && typeof val.length == 'number' && val.length > -1 && val.length % 1 == 0
            # beware of https://bugs.webkit.org/show_bug.cgi?id=142792
            if hasOwnProperty.call(val, 'callee') && !propertyIsEnumerable.call(val, 'callee')
              'arguments'
            else
              'array'
          else
            if toString.call(val) == '[object Date]'
              'date'
            else
              type
        break # fo' linting (linter cant see that all above paths return)
      else
        throw Error("Unknown object kind: #{val}")