text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  // NOTE: These type checking functions intentionally don't use `instanceof`
  // because it is fragile and can be easily faked with `Object.create()`.
  
  function isArray (arg) {
    if (Array.isArray) {
      return Array.isArray(arg)
    }
    return objectToString(arg) === '[object Array]'
  }
  exports.isArray = isArray
  
  function isBoolean (arg) {
    return typeof arg === 'boolean'
  }
  exports.isBoolean = isBoolean
  
  function isNull (arg) {
    return arg === null
  }
  exports.isNull = isNull
  
  function isNullOrUndefined (arg) {
    return arg == null
  }
  exports.isNullOrUndefined = isNullOrUndefined
  
  function isNumber (arg) {
    return typeof arg === 'number'
  }
  exports.isNumber = isNumber
  
  function isString (arg) {
    return typeof arg === 'string'
  }
  exports.isString = isString
  
  function isSymbol (arg) {
    return typeof arg === 'symbol'
  }
  exports.isSymbol = isSymbol
  
  function isUndefined (arg) {
    return arg === void 0
  }
  exports.isUndefined = isUndefined
  
  function isRegExp (re) {
    return objectToString(re) === '[object RegExp]'
  }
  exports.isRegExp = isRegExp
  
  function isObject (arg) {
    return typeof arg === 'object' && arg !== null
  }
  exports.isObject = isObject
  
  function isDate (d) {
    return objectToString(d) === '[object Date]'
  }
  exports.isDate = isDate
  
  function isError (e) {
    return (objectToString(e) === '[object Error]' || e instanceof Error)
  }
  exports.isError = isError
  
  function isFunction (arg) {
    return typeof arg === 'function'
  }
  exports.isFunction = isFunction
  
  function isPrimitive (arg) {
    return arg === null ||
           typeof arg === 'boolean' ||
           typeof arg === 'number' ||
           typeof arg === 'string' ||
           typeof arg === 'symbol' ||  // ES6 symbol
           typeof arg === 'undefined'
  }
  exports.isPrimitive = isPrimitive
  
  function objectToString (o) {
    return Object.prototype.toString.call(o)
  }
  
  function isPromise (promise) {
    return isObject(promise) && isFunction(promise.then) && isFunction(promise.catch)
  }
  exports.isPromise = isPromise
  