CoffeeScript Introspection Function

debug.coffee

debug = (obj, seen)->
  printProps = (obj)->
    #Edge case to handle is [1,2,3][9] = 'foo'
    #Need to factor the conditional out to check if the prop is a number less
    #than the array's length
    return ((if ! /^\d+$/.test prop then prop + ": " + debug(obj[prop], seen) \
      else '') for prop of obj).join(', ')

  seen = seen or []
  if obj in seen
    return '[Circular]'
  seen.push obj
  switch typeof obj
    when 'boolean'
      return obj.toString()
    when 'number'
      return obj.toString()
    when 'string'
      return obj.toString()
    when 'undefined'
      return 'undefined'
    when 'function'
      source = obj.toString()
      return source.slice(0, source.indexOf('{')) + ' {...}'
    else
      if Object.prototype.toString.call(obj) == Object.prototype.toString.call([])
        return '['+ ((debug(item, seen) for item in obj).join(', ')) + ']' + printProps obj
      else
        return (obj or 'null').toString() + printProps obj