_isKey.js

var isArray = require('./isArray'),
    isSymbol = require('./isSymbol');

/** Used to match property names within property paths. */
var reIsDeepProp = /\.|\[(?:[^[\]]*|(["'])(?:(?!\1)[^\\]|\\.)*?\1)\]/,
    reIsPlainProp = /^\w*$/;

/**
 * Checks if `value` is a property name and not a property path.
 *
 * @private
 * @param {*} value The value to check.
 * @param {Object} [object] The object to query keys on.
 * @returns {boolean} Returns `true` if `value` is a property name, else `false`.
 */
function isKey(value, object) {
  if (isArray(value)) {
    return false;
  }
  var type = typeof value;
  if (type == 'number' || type == 'symbol' || type == 'boolean' ||
      value == null || isSymbol(value)) {
    return true;
  }
  return reIsPlainProp.test(value) || !reIsDeepProp.test(value) ||
    (object != null && value in Object(object));
}

module.exports = isKey;