面试总结1

1 React 生命周期

2 hooks(useState, useEffect,

• useContext,=> createContext, useContext()
• useMemo,
  Returns a memoized value.
  , useMemo runs during rendering. Don’t do anything there that you wouldn’t normally do while rendering.
• useReducer,
  An alternative to useState. Accepts a reducer of type (state, action) => newState, and returns the current state paired with a dispatch method. (If you’re familiar with Redux, you already know how this works.)
  image.png

[Redux] creates one global state container which is above your whole application and is called a store.

[useReducer] creates an independent component co-located state container within your component.

• useRef, ref=input, createRef,ref.current.validate()
• useCallback
  Returns a memoized callback.
  useful when passing callbacks to optimized child components that rely on reference equality to prevent unnecessary renders (e.g. shouldComponentUpdate).
  useCallback(fn, deps) is equivalent to useMemo(() => fn, deps).

2.1 Fuction component vs class component

3 redux及项目中的使用

React is a library used to build user interfaces.
Redux - state management library for javascript applications.

image.png

React-redux official redux Ui binding library for react.

4 AWS pipeline

5 test 前后端

6 RDS and non-relational database

1. Data Strucutre

• NoSQL databases are designed to handle the more complex, unstructured data, (such as texts, social media posts, photos, videos, email).
• Relational databases were built during a time that data was mostly structured and clearly defined by their relationships.

2. Scaling

• Relaltional databases require a single server to host the entire database,
  3 Performance
  关系型数据库：缺点： 读写性能比较差，尤其是海量数据的高效率读写；

7 JWT

• header
• payload, 由我们需要发送的数据内容构成

• Singnature,签名由上面我们得到的header和payload的base64的字符串，通过.连接起来，然后使用HS256算法进行加密得到。

  
  image.png
• 缺点：由于jwt的payload是使用base64编码的，并没有加密，因此jwt中不能存储敏感数据。
  https://chengandpeng.github.io/2016/04/15/jwtvscookie/

8 React function compoent vs Class compoent