ReactJS FAQ’s
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ReactJS FAQ
2. What is JSX?
JSX is a syntax extension of JavaScript, it stands for JavaScript XML. It is used with React to describe what the user interface should look like. By using JSX, we can write HTML structures in the same file that contains JavaScript code.
3. What are the major features of React?
The Major features of React are :
- It uses server-side rendering.
- It uses the virtual DOM instead of the real DOM.
- It follows uni-directional data flow or data binding.
4. Why can’t the browsers read JSX?
Browsers can only read JavaScript objects. As JSX in not a regular JavaScript object, it is enable a browser to read JSX. First we have to transform JSX file into a JavaScript object using JSX transformers like Babel and then pass it to the browser.
5. What are the major advantages of React.
The major advantages of React are:
- React increases the application’s performance
- Due to JSX, code’s readability increases
- It convenient to use on the client as well as server side
- React is easy to integrate with other frameworks like Meteor, Angular, etc
- Using React, writing UI test cases become extremely easy
6. What is the purpose of render() in React.
Each React component must have a render() mandatorily. It returns a single React element which is the representation of the native DOM component. If more than one HTML element needs to be rendered, then they must be grouped together inside one enclosing tag such as , ,
7. What are the limitations of React?
Limitations of React are :
- It can be little difficult for the novice programmers to understand
- Coding gets complex as it uses inline templating and JSX
- React is just a library, not a full-blown framework.
- Its library is very large and takes time to understand.
8. What is Props?
Props is the shorthand for Properties in React. They are read-only components which must be kept immutable. They are always passed down from the parent to the child components throughout the application. A child component cannot send a prop back to the parent component. This helps in maintaining the unidirectional data flow and they are generally used to render the dynamically generated data.
9. What is a state in React and how is it used?
States are the heart of React components. They are the source of data and must be kept as simple as possible. States are the objects which determine components rendering and behavior. They are mutable unlike the props and create dynamic and interactive components. They are accessed via this.state().
10. What are synthetic events in React?
Synthetic events combine the response of different browser's native events into one API, ensuring that the events are consistent across different browsers.
The application is consistent regardless of the browser it is running in. Here, preventDefault is a synthetic event.
11. How do you implement React routing?
We can implement routing in React application by considering that have the components App, About, and Contact in our application.
12. What can you do with HOC?
HOC can be used for many tasks such as
- Render High jacking
- Code reuse, logic and bootstrap abstraction
- Props manipulation
- State abstraction and manipulation
13. What is the Flux?
Flux is the application architecture which Facebook uses for the building of web applications. It is a process of handling complex data inside a client-side application and manages how data flows in a React application.
14. What are Pure Components?
Pure components are the simplest and fastest components which can be written. They can replace any component which only has a render(). These components enhance the simplicity of the code and performance of the application.
15. What is React Router?
React Router is a routing library built on top of React, which is used to create routes in a React application.
16. What is the significance of keys in React?
Keys are used for identifying unique Virtual DOM Elements with their corresponding data driving the UI. They help React to optimize the rendering by recycling all the existing elements in the DOM. These keys must be a unique number or string, using which React just reorders the elements instead of re-rendering them. This leads to increase in application’s performance.
17. Why do we need to React Router?
React Router maintains consistent structure and behavior and is used to develop a single-page web applications. It enables multiple views in a single application by defining multiple routes in the React application.
18. What were the major problems with MVC framework?
The major problems with MVC framework :
- Applications were slow and inefficient
- DOM manipulation was very expensive
- There was huge memory wastage
- Due to circular dependencies, a complicated model was created around models and views
19. How are forms created in React?
React forms are similar to HTML forms. But in React, the state is contained in the state property of the component and is only updated via setState(). Thus the elements can’t directly update their state and their submission is handled by a JavaScript function. This function has full access to the data that is entered by the user into a form.
20. Why is it necessary to start component names with a capital letter?
In React, it is necessary to start component names with a capital letter. If we start the component name with small letter or lower case, it will throw an error as an unrecognized tag. It is because, in JSX, lower case tag names are considered as HTML tags.
ReactJS FAQ’s
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