在JavaScript中如何访问暂未存在的嵌套对象

const user = {
  id: 101,
  email: 'jack@dev.com',
  personalInfo: {
    name: 'Jack',
    address: {
      line1: 'westwish st',
      line2: 'washmasher',
      city: 'wallas',
      state: 'WX'
    }
  }
}

const name = user.personalInfo.name;
const userCity = user.personalInfo.address.city;

const user = {
  id: 101,
  email: 'jack@dev.com'
}

const name = user.personalInfo.name; // Cannot read property 'name' of undefined

const name = user && user.personalInfo ? user.personalInfo.name : null;

let city;
if (
  data && data.user && data.user.personalInfo &&
  data.user.personalInfo.addressDetails &&
  data.user.personalInfo.addressDetails.primaryAddress
  ) {
  city = data.user.personalInfo.addressDetails.primaryAddress;
}

const name = ((user || {}).personalInfo || {}).name;

const getNestedObject = (nestedObj, pathArr) => {
  return pathArr.reduce((obj, key) =>
    (obj && obj[key] !== 'undefined') ? obj[key] : null, nestedObj);
}

// 将对象结构作为数组元素传入
const name = getNestedObject(user, ['personalInfo', 'name']);

// 要访问嵌套数组，只需将数组索引作为数组元素传入。.
const city = getNestedObject(user, ['personalInfo', 'addresses', 0, 'city']);
// 这将从 addresses 中的第一层返回 city

import t from 'typy';

const name = t(user, 'personalInfo.name').safeObject;
const city = t(user, 'personalInfo.addresses[0].city').safeObject;
// address is an array