lodash/lang/isPlainObject.js

define(['../internal/getNative', '../internal/shimIsPlainObject'], function(getNative, shimIsPlainObject) {

  /** `Object#toString` result references. */
  var objectTag = '[object Object]';

  /** Used for native method references. */
  var objectProto = Object.prototype;

  /**
   * Used to resolve the [`toStringTag`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.prototype.tostring)
   * of values.
   */
  var objToString = objectProto.toString;

  /** Native method references. */
  var getPrototypeOf = getNative(Object, 'getPrototypeOf');

  /**
   * Checks if `value` is a plain object, that is, an object created by the
   * `Object` constructor or one with a `[[Prototype]]` of `null`.
   *
   * **Note:** This method assumes objects created by the `Object` constructor
   * have no inherited enumerable properties.
   *
   * @static
   * @memberOf _
   * @category Lang
   * @param {*} value The value to check.
   * @returns {boolean} Returns `true` if `value` is a plain object, else `false`.
   * @example
   *
   * function Foo() {
   *   this.a = 1;
   * }
   *
   * _.isPlainObject(new Foo);
   * // => false
   *
   * _.isPlainObject([1, 2, 3]);
   * // => false
   *
   * _.isPlainObject({ 'x': 0, 'y': 0 });
   * // => true
   *
   * _.isPlainObject(Object.create(null));
   * // => true
   */
  var isPlainObject = !getPrototypeOf ? shimIsPlainObject : function(value) {
    if (!(value && objToString.call(value) == objectTag)) {
      return false;
    }
    var valueOf = getNative(value, 'valueOf'),
        objProto = valueOf && (objProto = getPrototypeOf(valueOf)) && getPrototypeOf(objProto);

    return objProto
      ? (value == objProto || getPrototypeOf(value) == objProto)
      : shimIsPlainObject(value);
  };

  return isPlainObject;
});