What is React?
React is a front end JavaScript library developed by Facebook in 2011. It follows the component based approach which helps in building reusable UI components. It is used for developing complex and interactive web and mobile UI. Even though, it was open-so
What are the features of React?
It increases the application's performance
It can be conveniently used on the client as well as server side
Because of JSX, code's readability increases
React is easy to integrate with other frameworks like Meteor, Angular, etc
Using React, writing UI tes
What are the limitations of React?
React is just a library, not a full-blown framework
Its library is very large and takes time to understand
It can be little difficult for the novice programmers to understand
Coding gets complex as it uses inline templating and JSX
What is JSX?
JSX is a shorthand for JavaScript XML. This is a type of file used by React which utilizes the expressiveness of JavaScript along with HTML like template syntax. This makes the HTML file really easy to understand. This file makes applications robust and b
What do you understand by Virtual DOM? Explain its working.
A virtual DOM is a lightweight JavaScript object which originally is just the copy of the real DOM. It is a node tree that lists the elements, their attributes and content as Objects and their properties. React's render function creates a node tree out of
Steps of Virtual DOM
Whenever any underlying data changes, the entire UI is re-rendered in Virtual DOM representation.
Then the difference between the previous DOM representation and the new one is calculated.
Once the calculations are done, the real DOM will be updated with
Why can't browsers read JSX?
Browsers can only read JavaScript objects but JSX in not a regular JavaScript object. Thus to enable a browser to read JSX, first, we need to transform JSX file into a JavaScript object using JSX transformers like Babel and then pass it to the browser.
What do you understand from "In React, everything is a component.
Components are the building blocks of a React application's UI. These components split up the entire UI into small independent and reusable pieces. Then it renders each of these components independent of each other without affecting the rest of the UI.
Explain the purpose of render() in React.
Each React component must have a render() mandatorily. It returns a single React element which is the representation of the native DOM component. If more than one HTML element needs to be rendered, then they must be grouped together inside one enclosing t
What is Props?
Props are short hand for Properties in React. They are read-only components which must be kept pure i.e. immutable. They are always passed down from the parent to the child components through out the application. A child component can never send a prop ba
What is a state in React and how is it used?
States are the heart of React components. States are the source of data and must be kept as simple as possible. Basically, states are the objects which determine components rendering and behavior. They are mutable unlike the props and create dynamic and i
How can you update the state of a component?
State of a component can be updated using this.setState().
put in the object of the new state inside this.setState().
What is arrow function in React? How is it used?
Arrow functions are more of brief syntax for writing the function expression. They are also called 'fat arrow' (=>) the functions. These functions allow to bind the context of the components properly since in ES6 auto binding is not available by default.
What are the different phases of React component's lifecycle?
There are three different phases of React component's lifecycle:
Initial Rendering Phase: This is the phase when the component is about to start its life journey and make its way to the DOM.
Updating Phase: Once the component gets added to the DOM, it can
Explain the lifecycle methods of React components in detail.
Some of the most important lifecycle methods are:
componentWillMount() - Executed just before rendering takes place both on the client as well as server-side.
componentDidMount() - Executed on the client side only after the first render.
componentWillRece
What is an event in React?
In React, events are the triggered reactions to specific actions like mouse hover, mouse click, key press, etc. Handling these events are similar to handling events in DOM elements. But there are some syntactical differences like:
Events are named using c
List some of the cases when you should use Refs.
Following are the cases when refs should be used:
When you need to manage focus, select text or media playback
To trigger imperative animations
Integrate with third-party DOM libraries
How do you modularize code in React?
We can modularize code by using the export and import properties. They help in writing the components separately in different files.
How are forms created in React?
React forms are similar to HTML forms. But in React, the state is contained in the state property of the component and is only updated via setState(). Thus the elements can't directly update their state and their submission is handled by a JavaScript func
What are Higher Order Components(HOC)?
Higher Order Component is an advanced way of reusing the component logic. Basically, it's a pattern that is derived from React's compositional nature. HOC are custom components which wraps another component within it. They can accept any dynamically provi
What can you do with HOC?
HOC can be used for many tasks like:
Code reuse, logic and bootstrap abstraction
Render High jacking
State abstraction and manipulation
Props manipulation
What are Pure Components?
Pure components are the simplest and fastest components which can be written. They can replace any component which only has a render(). These components enhance the simplicity of the code and performance of the application.
What is the significance of keys in React?
Keys are used for identifying unique Virtual DOM Elements with their corresponding data driving the UI. They help React to optimize the rendering by recycling all the existing elements in the DOM. These keys must be a unique number or string, using which
What were the major problems with MVC framework?
Following are some of the major problems with MVC framework:
DOM manipulation was very expensive
Applications were slow and inefficient
There was huge memory wastage
Because of circular dependencies, complicated model was created around models and views
Explain Flux.
Flux is an architectural pattern which enforces the uni-directional data flow. It controls derived data and enables communication between multiple components using a central Store which has authority for all data. Any update in data throughout the applica
What is Redux?
Redux is one of the hottest libraries for front end development in today's marketplace. It is a predictable state container for JavaScript applications and is used for the entire applications state management. Applications developed with Redux are easy to
What are the three principles that Redux follows?
Single source of truth: The state of the entire application is stored in an object/ state tree within a single store. The single state tree makes it easier to keep track of changes over time and debug or inspect the application.
State is read-only: The on
What do you understand by "Single source of truth"?
Redux uses 'Store' for storing the application's entire state at one place. So all the component's state are stored in the Store and they receive updates from the Store itself. The single state tree makes it easier to keep track of changes over time and d
List down the components of Redux.
Redux is composed of the following components:
Action - It's an object that describes what happened.
Reducer - It is a place to determine how the state will change.
Store - State/ Object tree of the entire application is saved in the Store.
View - Simply
How are Actions defined in Redux?
Actions in React must have a type property that indicates the type of ACTION being performed. They must be defined as a String constant and you can add more properties to it as well. In Redux, actions are created using the functions called Action Creators
Explain the role of Reducer.
Reducers are pure functions which specify how the application's state changes in response to an ACTION. Reducers work by taking in the previous state and action, and then it returns a new state. It determines what sort of update needs to be done based on
What is the significance of Store in Redux?
A store is a JavaScript object which can hold the application's state and provide a few helper methods to access the state, dispatch actions and register listeners. The entire state/ object tree of an application is saved in a single store. As a result of
What are the advantages of Redux?
Advantages of Redux are listed below:
Predictability of outcome - Since there is always one source of truth, i.e. the store, there is no confusion about how to sync the current state with actions and other parts of the application.
Maintainability - The c
What is React Router?
React Router is a powerful routing library built on top of React, which helps in adding new screens and flows to the application. This keeps the URL in sync with data that's being displayed on the web page. It maintains a standardized structure and behavi
Why do we need a Router in React?
A Router is used to define multiple routes and when a user types a specific URL, if this URL matches the path of any 'route' defined inside the router, then the user is redirected to that particular route. So basically, we need to add a Router library to
What is react express?
Express is the wrapper for your node server.
What is axios?
Lightweight HTTP client based on the $http service within Angularjs.
Promise based and thus asynchronouse and wait forr readable asynchronous code. We can intercept and cancel requests. It's an easy to use API to make HTTP methods.