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React interview questions

React interview questions.

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1.

How does React work?

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2.

What is context?

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3.

What is virtual DOM?

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4.

What is props in ReactJS?

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5.

What is the use of refs?

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6.

What is JEST?

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7.

What are the advantages of ReactJS?

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8.

What is ReactJS?

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9.

How to write comments in ReactJS?

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10.

How would you write an inline style in React?

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11.

What are the major features of ReactJS?

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12.

What are props in React?

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13.

What are the differences between a class component and functional component?

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14.

Where in a React component should you make an AJAX request?

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15.

What is the difference between state and props?

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16.

What is the difference between a Presentational component and a Container component?

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17.

What are refs used for in React?

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18.

What's the difference between a controlled component and an uncontrolled one in React?

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19.

What are controlled components?

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20.

What is state in ReactJS?

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21.

When to use a Class Component over a Functional Component?

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22.

What does it mean for a component to be mounted in React?

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23.

How do we pass a property from a parent component props to a child component?

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24.

What are fragments?

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25.

When rendering a list what is a key and what is it's purpose?

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26.

How to create refs?

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27.

What happens when you call setState?

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28.

What are stateful components?

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29.

How would you prevent a component from rendering in React?

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30.

What is JSX?

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31.

How error boundaries handled in React (15)?

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32.

Where is the state kept in a React + Redux application?

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33.

What are the limitations of ReactJS?

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34.

What is the difference between React Native and React?

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35.

What are stateless components?

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36.

How is React different from AngularJS (1.x)?

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37.

What is the point of Redux?

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38.

Why is it necessary to capitalize the components?

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39.

What is the difference between state and props?

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40.

What is Flow?

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41.

How to create components in ReactJS?

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42.

What is the purpose of callback function as an argument of setState?

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43.

What are portals in ReactJS?

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44.

How to pass a parameter to an event handler or callback?

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45.

What’s the difference between an "Element" and a "Component" in React?

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46.

What happens during the lifecycle of a React component?

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47.

What is Flux?

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48.

What is the difference between component and container in react Redux?

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49.

What is inline conditional expressions?

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50.

How do you prevent the default behavior in an event callback in React?

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51.

What is reconciliation?

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52.

What is the purpose of using super constructor with props argument?

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53.

What happens when you call "setState"?

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54.

Describe how events are handled in React.

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55.

What is the difference between Element and Component?

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56.

What are Higher-Order components?

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57.

Name the different lifecycle methods.

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58.

What is a higher order component?

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59.

What is JSX?

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60.

What is state in react?

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61.

What are controlled components?

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62.

What is a store in redux?

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63.

How would you prevent a component from rendering?

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64.

What don't you like about React?

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65.

What advantages are using arrow functions?

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66.

Why is it advised to pass a callback function to setState as opposed to an object?

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67.

What's the typical pattern for rendering a list of components from an array of data?

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68.

What are PropTypes in React?

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69.

What are Pure Components?

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70.

What are the advantages of React over VueJS?

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71.

Name some popular Flux Libraries

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72.

What's the typical flow of data like in a React + Redux app?

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73.

What are synthetic events in ReactJS?

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74.

What's an alternative way to avoid having to bind to this in event callback methods?

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75.

What are some limitations of things you shouldn't do in the component's render method?

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76.

How to bind methods or event handlers in JSX callbacks?

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77.

What is useState() in React?

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78.

What is the difference between createElement and cloneElement?

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79.

Why fragments are better than container divs?

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80.

What is prop drilling and how can you avoid it?

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81.

What is an action?

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82.

What is the point of shouldComponentUpdate() method?

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83.

What are forward refs?

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84.

What do these three dots (...) in React do?

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85.

How do you tell React to build in Production mode and what will that do?

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86.

What are typical middleware choices for handling asynchronous calls in Redux?

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87.

What are the lifecycle methods of ReactJS?

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88.

What are the different phases of ReactJS component lifecycle?

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89.

What is Key and benefit of using it in lists?

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90.

What's the difference between an Element and a Component in React?

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91.

What is the difference between ShadowDOM and VirtualDOM?

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92.

Why do class methods need to be bound to a class instance?

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93.

What are stateless components?

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94.

What is ReactDOM?

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95.

What is children prop?

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96.

Why ReactJS uses className over class attribute?

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97.

What are React Hooks?

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98.

What does "shouldComponentUpdate" do and why is it important?

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99.

What's the difference between a "smart" component and a "dumb" component?

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100.

What is the render method for?

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101.

What is Lifting State Up in ReactJS?

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102.

Why should not we update the state directly?

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103.

How to set state with a dynamic key name?

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104.

What's the difference between useRef and createRef?

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105.

What is StrictMode in React?

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106.

What is the alternative of binding this in the constructor?

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107.

What is the difference between createElement and cloneElement?

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108.

What is the point of using keys in React?

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109.

What would be the common mistake of function being called every time the component renders?

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110.

What are advantages of using React Hooks?

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111.

What can you tell me about JSX?

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112.

What is the difference between HTML and React event handling?

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113.

What are error boundaries in ReactJS (16)?

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114.

What is reconciliation in React?

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115.

What are uncontrolled components?

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116.

What is equivalent of the following using React.createElement?

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117.

Given the code defined above, can you identify two problems?

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118.

What is a reducer?

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119.

What is the purpose of super(props)?

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120.

What is "Children"?

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121.

Why would you eject from create-react-app?

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122.

What is the difference between ReactJS and Angular?

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123.

Explain the Virtual DOM concept in React.

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124.

What is the difference between a controlled component and an uncontrolled component?

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125.

Which is preferred option with in callback refs and findDOMNode()?

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126.

What are the recommended ways for static type checking?

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127.

Describe Flux vs MVC?

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128.

Why would you use forceUpdate in a React component?

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129.

What is React Fiber?

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130.

What are some recent changes in the React library (e.g. in version 14, 15)?

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131.

Why does React use SyntheticEvents?

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132.

How would you go about investigating slow React application rendering?

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133.

What's a pure functional component in React?

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134.

What is the second argument that can optionally be passed to setState and what is its purpose?

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135.

When is it important to pass props to super(), and why?

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136.

Do Hooks replace render props and higher-order components?

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137.

Why would you need to bind event handlers to "this"?

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138.

What is the difference between Flow and PropTypes?

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139.

What is the difference between using constructor vs getInitialState in React?

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140.

Why are String Refs legacy?

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141.

Are you familiar with Flux?

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142.

What is the React context?

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143.

Why would you use React.Children.map(props.children, () => ) instead of props.children.map(() => )?

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144.

What is mapStateToProps and mapDispatchToProps?

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145.

How to create props proxy for HOC component?

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146.

How to conditionally add attributes to React components?

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147.

Does React re-render all components and sub components every time setState is called?

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148.

If you need to access the underlying DOM node for a React component, what's the typical way to do this in React?

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149.

How to apply validation on Props in ReactJS?

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150.

When would you use StrictMode component in React?

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151.

What is a Pure Function?

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152.

Explain some difference between Flux and AngularJS (1.x) approach

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153.

What is reselect and how it works?

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154.

What is the key architectural difference between a JavaScript library such as React and a JavaScript framework such as Angular?

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155.

What is Redux Thunk used for?

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156.

What is React Fiber?

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157.

How to use Polymer in ReactJS?

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158.

How to avoid the need for binding in React?

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159.

How does React renderer work exactly when we call setState?

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160.

If you created a React element like Twitter below, what would the component definition of Twitter look like?

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161.

What is wrong with this code?

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