4. What is state in React?

An internal data store (object) of a component. ...

Both Compiler and Transpilar ...

6. What does the "webpack" command do?

Webpack is a module bundler ...

A Library for building interaction interfaces ...

10. In React what is used to pass data to a component from outside?

Props are used to pass data to a component from outside ...

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React JS MCQ

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React JS Multiple choice interview questions (MCQ) - Test your React JS knowledge

1) To update state in react forcefully, which method is used

A. setState
B. forceUpdate

C. Both of above
D. None of above

2) What does ReactJS use to increase performance?

A. Virtual DOM

B. Original DOM
C. Local DOM
D. None of the Above

3) A valid react component can return ...... number of elements.

A. 1

B. 2
C. 3
D. None of the Above

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

A. It will be rendered as enabled

B. It will be rendered as disabled
C. It will not be rendered at all

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

A. getInitialState
B. render
C. renderComponent

D. None

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6) How many stages are there in React js life cycle

A. 1
B. 2
C. 3

D. 0

7) What does ReactJS cover?

A. Data layer in an application
B. User Interface layer in an application

C. Both A & B
D. All are Correct

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

A. only function component can have life cycle
B. Only class components can have life cycle

C. Both type of components can have life cycle
D. None of above

9) The state in react can be updated by call to setState method. These calls are

A. Synchronous in nature
B. Asynchronous in nature

C. Are asynchronous but can be made synchronous when required
D. None of above

10) What is a good use case for using a function while rendering a dynamic list of items

A. If we need to compute a value based on properties of items in the loop.

B. None. Functions should not be used while rendering a dynamic list.
C. To make the code shorter

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11) Which of the following is a correct definition of state in react?

A. A persistent storage
B. An internal data store (object) of component

C. Both
D. None

12) Regarding React js components, which of following statement is true?

A. function components can have state
B. function components are light weight

C. class components are light weight
D. class components are faster than function component

13) For uncontrolled components in react

A. Source of truth is DOM

B. Source of truth is component state
C. Source of truth can be anything
D. None of above

14) ReactJS uses _____ to increase performance

A. Virtual DOM

B. Original DOM
C. Both of above
D. None of above

15) Ref in react component is used to assign reference to DOM elements. Ref can be created by

A. Calling React.createRef method
B. Assigning a value to ref attribute in JSX
C. Both of above

D. None of above

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16) What is the second argument for setState useful for?

A. To invoke code after the setState operation is done

B. To replace the state completely instead of the default merge action
C. To access the previous state before the setState operation

17) For controlled components in react

A. Source of truth is DOM
B. Source of truth is component state

C. Source of truth can be anything
D. None of above

18) How many elements does a react component returns?

A. 1
B. 0
C. Multiple elements with one root element

D. None of the above

19) What are two ways data gets handled in react?

A. state & props

B. services & components
C. state & services
D. state & component

20) Number of elements, a valid react component can return

A. 1

B. 2
C. 3
D. 5

21) What are the limitations of ReactJS?

A. React is only for view layer of the app so we still need the help of other technologies to get a complete tooling set for development
B. React is using inline templating and JSX. This can seem awkward to some developers
C. The library of react is too large
D. All of these