链判断运算符(?.)

// 链判断运算符
    let zhangsan = {
      name: "zhangsan",
      girlFriend: {
        name: "lisi",
        boyFriend: {
          name: "wangwu"
        }
      }
    }

// let wangwu = zhangsan.girlFriend.boyFriend.name || "张三"
    let wangwu = (zhangsan && zhangsan.girlFriend && zhangsan.girlFriend.boyFriend && zhangsan.girlFriend.boyFriend.name)
    console.log(wangwu);

 // ?.来判断
 let name = zhangsan?.girlFriend?.boyFriend?.name || "张三"
 console.log(name);

实际截图: