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General React.js MCQs

1.

In relation to stateful React components, which of the following statements is correct?

i) React triggers the event handlers in the bubble phase, by default.

ii) For event handlers, CamelCase naming convention is used by React.

iii) React actually attaches event handlers to the DOM nodes themselves.

2. Which of the following is a React framework for creating animations?

3.

Which of the following options is the correct signature of the unmountComponentAtNodeO method that is used for removing a mounted React component from the DOM and Cleaning its event handlers and state?

4. Which of the following preprocessors is used by ReactJS to add XML syntax to JavaScript?

5. Which of the following methods is skipped on a component that triggered the update when the forceUpdate() method is called?

const numbers= [2, 4, 6, 8, 10];

const increased = ???((numbers) => number * 2);

console.log(increased);


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6.

In the below given code snippet, which of the following functions should be placed in place of "???" so that the values of numbers array are doubled?

const numbers= [2, 4, 6, 8, 10];

const increased = ???((numbers) => number * 2);

console.log(increased);

7.

In relation to React renderIntoDocument() function, which of the following options should be present globally before importing React?

i) window

ii) window.document

iii) window.document.createElement

8. Which Of the following is the correct signature of React testRenderer.update method that is used for re-rendering the in-memory tree with a new root element?

9.

Which of the following statements is! are correct about the ReactJS features?

1. In a ReactJS application, all components have a state.

2. ReactJS virtual DOM can differentiate between a static and a dynamic element.

3. Rendering is possible using a virtual DOM even without dirty checking.

10.

In relation to React test utilities, which of the following options is used for finding all DOM elements of components in the rendered tree that have DOM components with the matching tag name?

11.

Which of the following methods is first invoked in the component lifecycle's updating phase and is called when a component receives new properties from its parent component?

12.

While using React, which of the following commands is used for creating a new project?

13.

Which of the following statements is/are correct about ReactJS?

i) It is mandatory to use JSX in React development.


ii) One-way data flow is implemented by React.

14. In ReactJS, which of the following statements is correct about props parameter?

15. Which of the following React classes can implement: shouldComponentUpdate()?

16. Which of the following Lifecycle methods of ReactJS is a part of the update phase and not the initial phase?

17. Which of the following statements is NOT correct about the ReactDOM.render() method?

18. .In ReactJS, which of the following options is used for storing the read-only data that is passed from a parent, and that data belongs to the parent and cannot be changed by its children?

19. In relation to ReactJS Flux, which of the following options is used for specifying the changes that are triggered in an application?

20. Which of the following statements are correct about ReactJS forms?
isHidden: true,

title: 'React new Example'

}

Suppose the this.setState(nextState) method is called and the current state is updated to the following:

{

isHidden: false

}

Which of the following is the correct way in which React will merge these two states?


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21.

Consider the current state as following:

{

isHidden: true,

title: 'React new Example'

}

Suppose the this.setState(nextState) method is called and the current state is updated to the following:

{

isHidden: false

}

Which of the following is the correct way in which React will merge these two states?

22. In relation to ReactJS Flux function, how many and which of the following parameters are passed to the reducer function?

23.

While using React, keys help in the identification of which of the following options?

i) New added items.


ii) Removed items.


iii) Updated items.


iv) Total number of items.

24.

Which of the following statements is/are correct about the eslint-plugin-jsx-aiiy plugin?

i) It is used for providing AST tinting feedback regarding accessibility issues in the JSX.

ii) This plugin is provided by the Create React App with a subset of activated rules.

25. In relation to React Forms. which of the following attributes is used by the