lodash/_isKey.js

import isArray from './isArray';
import isSymbol from './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) {
  var type = typeof value;
  if (type == 'number' || type == 'symbol') {
    return true;
  }
  return !isArray(value) &&
    (isSymbol(value) || reIsPlainProp.test(value) || !reIsDeepProp.test(value) ||
      (object != null && value in Object(object)));
}

export default isKey;