React 面试题与答案

问题 26. What are controlled components in React?

Controlled components in React refer to the components that have the ability to maintain their state. The data is completely controlled by the parent component, and the current value is fetched by making use of props. This is done to notify about any change that occurs when using callbacks.

问题 27. Why is a router required in React?

A router is very much necessary in React as it is used to manage multiple routes whenever a user types in a URL. If the route is present in the router for that corresponding URL, then the user is taken to the particular route.

问题 28. What are the components of Redux in React?

Redux consists of four main components as shown below:

• Action: An object that describes the call
• Reducer: The state change storage unit
• Store: the state and object tree storage
• View: Displays data provided by the store

问题 29. What are the disadvantages of using MVC in React?

Among a plethora of advantages of using MVC in React, there are minor problems as stated below:

• A lot of memory wastage occurs.
• DOM manipulation costs a lot.
• The application becomes slow.
• Lots of dependencies are created.
• The complexity of models increases.

问题 30. What are pure components in React?

Pure components are singular entities that are written in React. They are fast and simple to write and have the ability to replace a component that has only the render() function. This is done to ensure that the performance of the application is good and that the code is kept simple at the same time.