Infosys Certified React Native Developer
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Join Premium10 Infosys Certified React Native Developer practice questions with answers
Real Lex exam-pattern multiple-choice questions for the Infosys Certified React Native Developer certification. Each question includes the correct answer. The full question bank is available to Premium members.
- Question 1
Reena installed ionic native, but she is getting the following error while trying to preview the application over browser:
Native: tried calling Statusbar.styleDefault, but cordova is not available
How can this be resolved?- ✓
Execute the commands:
ionic cordova platform add browser
ionic cordova run browser
Correct - B
Execute the commands:
ionic cordova set browser
ionic cordova run browser
- C
Execute the commands:
ionic cordova platform set browser
ionic cordova run browser
- D
Execute the commands:
ionic cordova add browser
ionic cordova platform run browser
- ✓
- Question 2
Which statements from below are TRUE about keys in React. Select all options that are applicable.
- ✓ Keys are used to identify unique Virtual DOM elements that are driving the UI. Correct
- B Keys are optional attribute in components.
- C Since it is optional attribute in components React will not throw any warning for it and thus it is good to ignore adding any keys in JSX.
- D Keys can be given any values like unique number or string, thus I can provide timestamp as a value to keys attribute.
- E Keys help React to optimize the rendering cycle.
- Question 3
Alex wants to build a native mobile application. He wants to use React Native to code the application. Select the appropriate option from below:
- ✓ Same code will work on all OS Correct
- B Same code will work only on Android and iOS
- C Have to code separately for each mobile OS
- D Can only create Android apps using React Native
- Question 4
Dom wants to create a mobile banking application which needs to be highly secure. Which of the following would you normally chose to build it?
- ✓ React Native Correct
- B Kotlin
- C Xamarin
- D Swift
- Question 5
If React Native is creating pure native app and the built app (i.e, .apk, or .ipa) has javascript bundle in it , then how is the app a pure native app. Identify the CORRECT statement from below.
- ✓ React native doesn’t create a pure native app. It runs the bundles javascript bundle in the webview of the native platfrom. Thus it is just wrapping the javascript in a native executable container Correct
- B React native compiles and builds the javascript into native components, and thus the end ipa or apk doesn’t contain the bundle file rather the it contains the native corresponding code , ie. Objective-c / swift code or java code in case of Android
- C React native uses the React Native’s Bridge layer to serialize,batch commands for native layer, for the javascript implemented components. It uses the javascript runtime provided by the native platform to do it without blocking the UI thread
- D React Native uses internally Apache cordova to create native app (i.e apk, ipa )
- Question 6
Is setState() an async operation? If yes, why is it async operation.
- ✓ setState is a not a async operation. setState update the state property as soon as it is called in the operation thus triggering a re-render of the component. Correct
- B setState is a async operation. React batches the setState operations for performance gains. This causes the state property to update and thus re-rendering of component. Making it sync is an expensive operation and may leave the browser or native platform unresponsive.
- C setState is a synchronous operation. It has to be synchronous because as soon as we update the state value we want it to be reflected on screen. Otherwise user will not see the right date on screen.
- D setState is not at all async operation because we are not calling any external resource in setState. So it can’t be async operation.
- Question 7
Which of these statements is/are TRUE for state and props.
- ✓ Both state and props can receive initial value from parent components. Correct
- B Both state and props can be set with default values inside components.
- C Both state and props can be changed ( i.e, assigned different values) inside the component.
- D Parent component can change the value of both state and props.
- Question 8
Raj was trying to figure out the flex property of React native.
import React, { Component } from 'react';
import { View, Text, StyleSheet } from 'react-native';
import { Constants } from 'expo';export default class App extends Component {
render() {
return (
<View style={styles.container}>
<View style={[styles.layout, styles.rowStretch]}>
<Text>
This is my sample test statement which i am using to test this
concept.
</Text>
</View>
<View style={[styles.layout, styles.columnStretch]}>
<Text>
This is another sample test statement which i am using to test this concept.
</Text>
</View>
</View>
);
}
}const styles = StyleSheet.create({
container: {
paddingTop: Constants.statusBarHeight,
flex: 1,
flexDirection: 'row',
},
layout: {
flex: 1,
padding: 15,
marginBottom: 5,
backgroundColor: 'whitesmoke',
flexDirection: 'row',
},
rowStretch: {
flexDirection: 'row',
justifyContent: 'space-between',
alignItems: 'stretch',
},
columnStretch: {
flexDirection: 'row',
justifyContent: 'space-between',
alignItems: 'stretch',
},
});Choose the most appropriate output.
- ✓ The code will execute without any errors and both statements will be displayed in the same row as two coloumns Correct
- B The code will execute without any errors and both statements will be displayed in the different rows
- C The code will execute without any errors but only the first statement will be displayed
- D The code will run into errors
- Question 9
Which of these is the CORRECT statement for ‘ref’ in React?
- ✓ Ref is added to the DOM element or an instance of a component to access it directly. It takes function as value which will receive the underlying DOM element or the mounted instance of the component as its first argument.. Correct
- B Ref is only available in React.js and not in React-Native.
- C Ref cannot be applied to the React Native’s core components.
- D Ref is a way to access DOM element or instance of a component. It can be assigned a javascript object which the element can access as well.
- Question 10
Which is the CORRECT statement with respect to 'StyleSheet.create'?
- ✓ This method ensures that the style values created are immutable and opaque and they are only created once Correct
- B Stylesheet.create is method that can implement a function which takes javascript object as argument for the function
- C Stylesheet.create method is very performance intensive operation and should be used carefully
- D Stylesheet is imported from react package which also works well with React Native
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