var ObjProto = Object.prototype

exports.isEmpty = isEmpty
exports.isArray = Array.isArray || isArray
exports.isObject = isObject
exports.has = has

function isEmpty (obj) {
  if (obj == null) return true
  if (isArray(obj) ||
     (typeof obj === 'string')) return (obj.length === 0)
  for (var key in obj) if (has(obj, key)) return false
  return true
}

function isArray (obj) {
  return ObjProto.toString.call(obj) === '[object Array]'
}

function isObject (obj) {
  return typeof obj === 'function' || typeof obj === 'object' && !!obj
}

function has (obj, key) {
  return ObjProto.hasOwnProperty.call(obj, key)
}