text: What Is Reactjs?
  The List of Major Features as following -
  But there are only some syntactical differences and it looks like -
  Example looks like -. className="mycompo">
  
  2. Mouse Click
  3. Key Press
  4. And too many
  But there are only some syntactical differences and it looks like -
  1. Events are named using camel case instead of just using the lowercase.
  2. Events are passed as functions instead of strings.
  The event argument contains a set of properties and its behavior that is accessed via its event handler only.
  The Example -
  // In HTML
  <button onclick="clickMe()">Click Me!</button>
  //In React
  class Display extends React.Component({
  show(evt) {
  // TODO; your code
  },
  render() {
  // Render the button with event - onClick
  return (
  <button onClick={this.show}> Click Me!</button>
  );
  }
  });
  What Is Synthetic event?
  The Synthetic Event is a cross browser wrapper around browser’s native event.
  Example looks like -
  class DisplayAlert extends Component {
  alertMe() {
  alert("Hey, I am alert!");
  }
  render() {
  return (
  <button onClick={this.alertMe}>show alert </button>
  );
  }
  }
  export default DisplayAlert;
  What Are the differences between Controlled and Uncontrolled Components?
  Controlled Components –
  1. The controlled components not maintain their own state.
  2. The data is controlled by the parent component.
  Uncontrolled Components -
  1. The uncontrolled components maintain their own state.
  2. The data is controlled by the DOM
  What Is Higher Order Components (HOC)?
  Higher Order Component (HOC) is patterns, pure, and custom components that is derived from Reactjs compositional nature and provide advanced ways of reusing your components logic.
  What can you do with HOC?
  Higher Order Component (HOC) can be used for -
  1. Code reusability
  2. State abstraction and manipulation
  3. Bootstrap abstraction
  4. Props manipulation
  5. Render High jacking
  6. And may more
  What Is Component in Reactjs?
  Components are the heart of Reactjs and components let us split the user interface (UI) into independent, reusable pieces.
  Create a new component class using React.createClass. When you create a new components call, you must implement render() function.
  The example for the components is -
  var HiMsg = React.createClass({
  render: function() {
  return <div>Hello, My name is - {this.props.name}</div>;
  }
  });
  ReactDOM.render(
  <HiMsg name="msg" />,
  document.getElementById('container')
  );
  What Is Controllable Component in Reactjs?
  A controlled component is a component where React is in control and takes the value through Props and changes are notified to the parent component through callbacks.
  Parent component controls this component either by passing the data and handling the callbacks and managing its own state.
  What Is Uncontrollable Component in Reactjs?
  Uncontrollable component is a component which stores its own state internally.
  What Are Pure Components?
  Pure components are the simplest and fastest components which can be written and it can replace any component which only has a render ().
  These components increase the performance and code simplicity of the application.
  How to update the State of the Component in Reactjs?
  In the Reactjs, you can update the State of the components by using the method – setState()
  What Are the Component Life Cycle methods in Reactjs?
  The list of Component Life Cycle Methods -
  1. constructor() method
  2. componentWillMount() method
  3. componentDidMount() method
  4. render() method
  5. componentWillUpdate() method
  6. componentDidUpdate() method
  7. componentWillUnMount() method
  What Are the methods called when Component is created or while inserting it to DOM?
  The list Methods as following -
  1. constructor() method
  2. componentWillMount() method
  3. render() method
  4. componentDidMount() method
  What Are the methods called when State or Props of the Component is changed?
  The list Methods as following -
  1. componentWillReceiveProps()
  2. shouldComponentUpdate()
  3. componentWillUpdate()
  4. render()
  5. componentDidUpdate()
  In which lifecycle event do you make AJAX requests and why?
  The Ajax requests should go away in the componentDidMount life-cycle event.
  What Is React Router?
  React Router is a powerful routing library built on top of React, which helps in adding new screens, developing single page application and flows to the application.
  React Router keeps the URL in sync with data which displayed on the web page and also maintains a standardized structure and behavior.
  React Router has a simple API.
  Why do we need a Router in Reactjs?
  A Router is used to define multiple routes and when a user types a specific URL.
  We need to add a Router library in your apps that allows you to creating multiple routes with each leading to us a unique view.
  When would you use a Class Component over a Functional Component?
  If your component has state, a lifecycle methods or a class component, you should use a functional component.
  What Is difference between setState and forceUpdate () and findDOMNode () in Reactjs?
  1. setState() - It is used to update the state of the component. It will only add changes to the original state.
  2. forceUpdate() - It is used to forceUpdate the state of the component. It will only update to the original state.
  3. findDOMNode() - It is used to forceUpdate the state of the component. It will only update to the original state.
  How to use Loop in Reactjs?
  let rows = [];
  for (var i = 0; i < numrows; i++) {
  rows.push(<objectrow key="{i}">);
  }
  return tbody(rows); </objectrow>
  How to set focus in Reactjs?
  class App extends React.Component{
  componentDidMount(){
  this.nameInput.focus();
  }
  render() {
  return(
  <div>
  <input defaultvalue="Won't focus" />
  <input ref="{(input)" /> { this.nameInput = input; }}
  </div>
  );
  }
  }
  What Are the components in Flux architecture?
  1. Action
  2. Dispatcher
  3. Store
  4. View
  What Are the popular libraries used for Flux?
  1. Redux
  2. Reflux
  3. Alt
  What Are refs in React and why are they important?
  Refs are used to return the reference to our element and allow you to get direct access to DOM elements.
  Refs should be avoided but they are useful when you adding the methods to components.
  The example is -
  class UnControlledForm extends Component {
  handleSubmit = () => {
  console.log("My Input Value is -", this.input.value)
  }
  render () {
  return (
  <form onSubmit={this.handleSubmit}>
  <input type='text' ref={(input) => this.input = input} />
  <button type='submit'>Submit</button>
  </form>
  )
  }
  }
  What Are keys in Reactjs and why are they important?
  Reactjs keep track of what items have changed, been added and been removed from a list.
  The example looks like -
  render () {
  return (
  <ul>
  {
  this.state.todoItems.map(({task, uid}) => {
  return <li key={uid}>{task}</li>
  })}
  </ul>
  )