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For RJS developers, those who are preparing for the interview this blog can be proven of great help. This blog contains top interview questions and answers that are mostly asked by the interviewers.
React is one of the most in-demand skills in the IT world today. It is one of the most used JavaScript tools that is used to develop an application or website and React is considered as the fastest growing framework.
Here, we will give you an overview of the market status of this framework and then will cover the questions and answers that will help you in understanding the JavaScript as a framework.
ReactJS is a front-end JavaScript library and was developed by Facebook in 2011. Designers can build reusable components through ReactJS. Interactive and complex mobile and web UI can be developed by ReactJS and is an open source framework. ReactJS also has the largest supporting community.
GitHub has more than 1,000 contributors for ReactJS. Favorite features of ReactJS for frontend developers are virtual DOM and reusable components. Due to its features, it is giving strong competition to other frameworks like AngularJS, Metro, Vue, etc.
ReactJs is a front-end JavaScript library and provides a component-based approach that helps designers to build reusable components. React has following listed features:
React is one of the most used libraries and has following listed advantageous features:
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Though React is a popular tool but has some limitations that are listed below:
Virtual DOM is nothing but it is just a copy of real DOM. In the node tree of Virtual DOM, all elements, attributes, and content are listed as objects and its properties. Through render function, a node tree is created by the React components. After mutation, the tree gets updated and it may happen due to system user’s action.
Real DOM | Virtual DOM |
It can directly update the HTML | It cannot update HTML directly |
Manipulation in Real DOM is much expensive | DOM manipulation is quite easier |
Update is slower | Update is faster |
Memory wastage is higher | Memory is not wasted |
A new DOM is created when elements are updated | JSX is updated when an update happens |
JSX stands for JavaScript XML, it is just a file that is used by React and is written in JavaScript and HTML. Due to this HTML file becomes easy to understand and applications become robust and their performance is increased. Below syntax is used by this file:
Render () {
return (
<div>
<H1> Hello World!!!!</H1>
</div>
);
}
JSX is not purely JavaScript objects and browsers can only read JavaScript objects. So, if we want that a JSX file must be read by the browser then we will have to convert it into a JavaScript object and for that, we will have to use JSX transformers like pass or Babel and then it will be passed to the browser.
Each component of React needs to be rendered by using render () function. To group more than one HTML element we can use <form>, <group>, <div> etc. It then returns to single react element that represents native DOM component. This function of render must return the same result whenever it has been invoked.
React and Angular are two of the most popular libraries for JavaScript and let us have a quick look at differences between them:
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The building blocks of the React application UI are called components. Entire UI is divided into several components that are smaller in size and are reusable as well. Then each of these components is rendered independently without affecting rest of the UI.
In React, Props is used for Properties. These are immutable components of React that have to be kept pure. These components are always passed to the child components from parent components and cannot be sent back to the parent component. It makes the data-flow unidirectional and dynamically generated data is rendered through this concept.
States are basically data source in React and are kept as simple as possible. Through states, the rendering and behavior of the components are identified. Unlike props, they are mutable and can be used to create interactive and dynamic components. Usually, this.state() function is used to access them.
Following are a few noticeable points for a quick comparison of prop and state:
class newComponent extends React.Component{
render(){
return(
<div>
<h1>Welcome</h1>
<Header/></div>
); } }
class Header extends React.Componet{
Render(){return (Header Component </h1>
); } }
ReactDOM.render(<newComponent/>, document.getElementById(‘content’));
Class newComponent extends React.Component{
Constructor(){
Super();
This.state={name: ‘Maxx’, id: ‘101’} }
Render()
{setTimeout(()=>{this.setState({name:’Denis’, id:’222’})},2000)
Return(
<div>
Welcome {this.state,name}
What is id {this.state.id}
</div>
);}}
ReatDOM.render(<newComponent/>, document.getElementById(‘content’)
Following are the main considerable differences between stateful and stateless components:
In the lifecycle of React’s component, there are following three phases:
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In the entire lifecycle of a React component, the following methods are used to accomplish the functions:
The number of questions that can be asked to any fresher or experienced ReactJS professionals. Other commonly asked concepts and terms are Redux, an event of React, HOC, Pure component, keys in React, Reducer and many more. One must keep updating his knowledge to qualify the interview. We at JanBask Training have prepared the list of questions carefully and answered each of the questions after careful observation only.
We wish you luck for your next interview! Happy Job Hunting!
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