React – Quiz – Learning Portal

Everything in React is a ____________?

Class
Function
Component
Module

What would be the output of the following example?
var Helloword=(props)=> {
return(
<div>
Hello World 1
</div>
<div>
Hello World 2
</div>
);
}
ReactDOM.render(<Helloworld/>,mountNode)

Hello World 1
Hello World 2
Hello World 1 Hello World 2
Error

What is the default port where webpack-server runs?

3000
8080
3030
6060

What is a state in React?

A permanent storage.
Internal storage of the component.
External storage of the component.
None of the above.

What are the two ways to handle data in React?

State & Props
Services & Components
State & Services
State & Component

Does React.js create a VIRTUAL DOM in the memory?

True
False

Which of the following is used to pass data to a component from outside in React.js?

SetState
Render with arguments
Props
PropTypes

Which of the following method refers to the parent class in React.js?

inherits()
self()
super()
this()

How can you set a default value for an uncontrolled form field?

By using the value property
By using the defaultValue property
By using the default property
It is assigned automatically.

Name the function used to change the state of react component.

this.setState
this.setChangeState
this.State{}

How can you access the state of a component from inside of a member function?

this.state
this.values
this.getState()
this.prototype.stateValue

ReactJS covers _________

User Interface layer in an application
Data layer in an application

With JSX you can write expressions inside?

()
[]
" "
{}

Which of the following API is a MUST for every ReactJS component?

getInitialState
render
renderComponent
None

What is the second argument for setState useful for?

To invoke code after the setState operation is done
To replace the state completely instead of the default merge action
To access the previous state before the setState operation

How many stages are there in React js life cycle?

1
2
3
0

In relation to React js component lifecycle, which statement is true

only function component can have life cycle
Only class components can have life cycle
Both type of components can have life cycle
None of above

Keys are given to a list of elements in react. These keys should be.

Unique in the DOM
Unique among the siblings only
Do not requires to be unique
None of above

Which of the following is correct syntax for a button click event handler, foo?

<button onclick={this.foo()}>
<button onclick={this.foo}>
<button onClick={this.foo()}>
<button onClick={this.foo}>

How do you write an inline style specifying the font-size:12px and color:red; in JSX?

style={{font-size:12,color:'red'}}
style={{fontSize:'12px',color:'red'}}
style={fontSize:'12px',color:'red'}
style={{font-size:12px,color:'red'}}

Props in React can ________

Be modified inside the component
Not be modified in the component
Be modified in another component
None of the above

Broswers cannot read JSX?

True
False

Which of the following are the advantages of React.js?

React.js can increase the application's performance with Virtual DOM.
React.js is easy to integrate with other frameworks such as Angular, BackboneJS since it is only a view library.
React.js can render both on client and server side.
All of the above

Which of the following acts as the input of a class-based component?

Class
Factory
Render
Props

Which of the following keyword is used to create a class inheritance?

Create
Inherits
Extends
This

Which of the following is not a correct way of declaring variables?

var val = 0;
const val = 0;
let val = 0;
int val = 0;

What will happen if you render an input element with disabled = {false} ?

It will be rendered as disabled
It will not be rendered at all
It will be rendered as enabled
You cannot set it false.

Which of the following lifecycle events React components have at the highest level?

Destruction
Initialization
State/Property Updates
All of the above.

Which of the following best defines the “key” prop?

"Key" prop is used to look pretty, and there is no benefit whatsoever.
"Key" prop is a way for React to identify a newly added item in a list and compare it during the "diffing" algorithm.
It is one of the attributes in HTML.
It is NOT commonly used in an array.

What changes would appear in the component as soon as the state of the React component is changed?

It will do nothing; you have to call render method to render the component again.
It will re-render the component.
It can be created again from scratch.
None of the above.

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