Git: How to clone only part of the repo (specific directory)

 https://stackoverflow.com/a/60729017/5721873

ES6 Class Singleton pattern

 Regular class pattern:

Restructure with static method:

JavaScript: What is 'this'?

• 宣告的位置不重要，重要的是呼叫的方法
• https://zhuanlan.zhihu.com/p/23804247