1  // Copyright Joyent, Inc. and other Node contributors.
  2  //
  3  // Permission is hereby granted, free of charge, to any person obtaining a
  4  // copy of this software and associated documentation files (the
  5  // "Software"), to deal in the Software without restriction, including
  6  // without limitation the rights to use, copy, modify, merge, publish,
  7  // distribute, sublicense, and/or sell copies of the Software, and to permit
  8  // persons to whom the Software is furnished to do so, subject to the
  9  // following conditions:
 10  //
 11  // The above copyright notice and this permission notice shall be included
 12  // in all copies or substantial portions of the Software.
 13  //
 14  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 15  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 16  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
 17  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 18  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 19  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 20  // USE OR OTHER DEALINGS IN THE SOFTWARE.
 21  
 22  // NOTE: These type checking functions intentionally don't use `instanceof`
 23  // because it is fragile and can be easily faked with `Object.create()`.
 24  
 25  function isArray(arg) {
 26    if (Array.isArray) {
 27      return Array.isArray(arg);
 28    }
 29    return objectToString(arg) === '[object Array]';
 30  }
 31  exports.isArray = isArray;
 32  
 33  function isBoolean(arg) {
 34    return typeof arg === 'boolean';
 35  }
 36  exports.isBoolean = isBoolean;
 37  
 38  function isNull(arg) {
 39    return arg === null;
 40  }
 41  exports.isNull = isNull;
 42  
 43  function isNullOrUndefined(arg) {
 44    return arg == null;
 45  }
 46  exports.isNullOrUndefined = isNullOrUndefined;
 47  
 48  function isNumber(arg) {
 49    return typeof arg === 'number';
 50  }
 51  exports.isNumber = isNumber;
 52  
 53  function isString(arg) {
 54    return typeof arg === 'string';
 55  }
 56  exports.isString = isString;
 57  
 58  function isSymbol(arg) {
 59    return typeof arg === 'symbol';
 60  }
 61  exports.isSymbol = isSymbol;
 62  
 63  function isUndefined(arg) {
 64    return arg === void 0;
 65  }
 66  exports.isUndefined = isUndefined;
 67  
 68  function isRegExp(re) {
 69    return objectToString(re) === '[object RegExp]';
 70  }
 71  exports.isRegExp = isRegExp;
 72  
 73  function isObject(arg) {
 74    return typeof arg === 'object' && arg !== null;
 75  }
 76  exports.isObject = isObject;
 77  
 78  function isDate(d) {
 79    return objectToString(d) === '[object Date]';
 80  }
 81  exports.isDate = isDate;
 82  
 83  function isError(e) {
 84    return (objectToString(e) === '[object Error]' || e instanceof Error);
 85  }
 86  exports.isError = isError;
 87  
 88  function isFunction(arg) {
 89    return typeof arg === 'function';
 90  }
 91  exports.isFunction = isFunction;
 92  
 93  function isPrimitive(arg) {
 94    return arg === null ||
 95           typeof arg === 'boolean' ||
 96           typeof arg === 'number' ||
 97           typeof arg === 'string' ||
 98           typeof arg === 'symbol' ||  // ES6 symbol
 99           typeof arg === 'undefined';
100  }
101  exports.isPrimitive = isPrimitive;
102  
103  exports.isBuffer = Buffer.isBuffer;
104  
105  function objectToString(o) {
106    return Object.prototype.toString.call(o);
107  }