chai/lib/chai/utils/type.js

BDD/TDD assertion library for node.js and the browser. Test framework agnostic.

/*!
 * Chai - type utility
 * Copyright(c) 2012-2013 Jake Luer <jake@alogicalparadox.com>
 * MIT Licensed
 */

/*!
 * Detectable javascript natives
 */

var natives = {
    '[object Arguments]': 'arguments'
  , '[object Array]': 'array'
  , '[object Date]': 'date'
  , '[object Function]': 'function'
  , '[object Number]': 'number'
  , '[object RegExp]': 'regexp'
  , '[object String]': 'string'
};

/**
 * ### type(object)
 *
 * Better implementation of `typeof` detection that can
 * be used cross-browser. Handles the inconsistencies of
 * Array, `null`, and `undefined` detection.
 *
 *     utils.type({}) // 'object'
 *     utils.type(null) // `null'
 *     utils.type(undefined) // `undefined`
 *     utils.type([]) // `array`
 *
 * @param {Mixed} object to detect type of
 * @name type
 * @api private
 */

module.exports = function (obj) {
  var str = Object.prototype.toString.call(obj);
  if (natives[str]) return natives[str];
  if (obj === null) return 'null';
  if (obj === undefined) return 'undefined';
  if (obj === Object(obj)) return 'object';
  return typeof obj;
};