我正在学习ES6代理，为此，我遵循javascript.info的指南，下面的示例，避免阅读，删除，添加新属性和列出属性，如果属性名称以下划线开头，例如_password

let user = {
  username: "john.doe",
  firstname: "John",
  lastname: "doe",
  email: "john.doe@example.com",
  _password: "******"
};

user = new Proxy(user, {
  get(target, property) {
    if (property.startsWith("_")) {
      throw new Error("Access denied");
    }

    return target[property];
  },

  set(target, property, value) {
    if (value.startsWith("_")) {
      throw new Error("Access denied");
    }

    target[property] = value;

    return true;
  },

  deleteProperty(target, property) {
    if (property.startsWith("_")) {
      throw new Error("Access denied");
    }

    delete target[property];

    return true;
  },

  ownKeys(target) {
    return Object.keys(target).filter(key => !key.startsWith("_"));
  }
});

const { username, firstname, lastname, email } = user;

console.log(username, firstname, lastname, email);
console.log(JSON.stringify(user, null, 2));
console.log(user);

对console.log(JSON.stringify(user, null, 2));的调用显示了预期的输出，因为输出中省略了_password

{
    "username": "john.doe",
    "firstname": "John",
    "lastname": "doe",
    "email": "john.doe@example.com"
}

但是当调用console.log(user);时，我得到以下错误

/tmp/index.js:48
    if (property.startsWith("_")) {
                 ^

TypeError: property.startsWith is not a function

谢谢你的评论