Module Summary模块总结

Congratulations! You have completed this module. At this point in the course, you know:
恭喜！您已完成本模块。在课程的这个阶段，您已经知道：

• Asynchronous network operations can be handled using callback functions in order to prevent blocking JavaScript code  
  异步网络操作可以使用回调函数来处理，以防止阻塞 JavaScript 代码
• A callback function must invoke another callback function to pass a message from the Node.js module back to the main application after the Node.js module receives a response message 
  回调函数必须在 Node.js 模块接收到响应消息后，调用另一个回调函数，将消息从 Node.js 模块传递回主应用程序
• Nested callbacks can be difficult to read and debug. Inversion of control causes trust issues when dealing with third-party code 
  嵌套回调难以阅读和调试。控制反转在处理第三方代码时会引起信任问题
• Promise objects are most useful for operations that are time-consuming and can block resources 
  承诺对象对于耗时且可能阻塞资源的操作最有用
• JSON.parse() and JSON.stringify() are two methods used to parse JSON objects 
  JSON.parse() 和 JSON.stringify() 是两个用于解析 JSON 对象的方法