判断是否为Plain Object(Plain Object意为用JSON形式定义的普通对象或者new Object()创建的简单对象)

isPlainObject.js

/**
 * @param {any} obj The object to inspect.
 * @returns {boolean} True if the argument appears to be a plain object.
 */
function isPlainObject(obj) {
  if (typeof obj !== 'object' || obj === null) return false;

  let proto = obj;
  while (Object.getPrototypeOf(proto) !== null) {
    proto = Object.getPrototypeOf(proto);
  }

  return Object.getPrototypeOf(obj) === proto;
}