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How to Learn React in 2022

One of the biggest challenges that all front-end developers face is building responsive and complex UI, while retaining high load time and enhancing performances. The User Interface is what grabs the attention of the users and increases the popularity of your website. A website that is slow and takes a lot of time to get loaded will be abandoned more often than not. In this respect React is a bestselling tool for developers, as it ensures better user experience and optimizes app performances.  Though it sounds very cool, learning a new technology can be a daunting prospect. A planned approach can be extremely helpful while learning new skills. Before we start, let us look at what we will learn in this blog! Introduction to React React VS Other frameworks React prerequisites Approach to mastering a skill Online learning process Roadmaps to learn React Fundamentals Why should I learn React? Challenges while learning ConclusionIntroduction to React: React is a powerful JavaScript Library, created by Facebook. It is open source and a component-based UI library tool. All the elements which we see in a website built on React are composed of several sub-components e.g., the buttons, side menus, navigation bar, headers, footers, paragraphs etc. To know about more about the components and other features you should check out this official documentation at.React VS other Frameworks/Libraries The frameworks for Web development are: Angular Angular is an application design framework (not a JS Library) which is based on TypeScript and is open source. It is maintained and managed by the Angular Team at Google and can be used to create efficient Single Page Applications (SPAs) for enterprises. Pros: Easily create Single Page Applications Prototyping, Development, and testing becomes faster It supports 2-way data binding DOM Manipulation is easy and hence server-side load is minimized Responsive web designing Latest Angular versions support TypeScript which makes it easier to learn Good community support Cons: Challenging to understand MVC for beginners Some features are difficult to understand e.g., dependency injection, services etc. Poor response during Search Engine Optimization Official Documentation Link. Vuejs It is a JavaScript-based UI framework. It is used for building user interfaces and creating Single Page Applications with the help of some libraries. Pros: Remarkably simple to use It has good documentation It supports virtual DOM Manipulation and 2-way Data binding Unit testing can be efficiently done Good community support Cons: It is not suitable for large-scale projects Limited resources Not immensely popular among developers Official Documentation Link.There are several other JS libraries and frameworks in the market. Click the links below to know more about these libraries or frameworks. jQuery Official Documentation Link. Emberjs Official Documentation Link.Backbonejs Official Documentation Link.Semantic-UI Official Documentation Link.Foundation Official Documentation Link.Svelte Official Documentation Link.Here’s what makes React more powerful than others: It is based on Components, and the same components can be reused We can break the whole UI into smallest components It is simple to use One-way data binding It uses virtual DOM, that means there is lesser load in the server-side rendering High performance Good documentation Downsides of React JSX is very confusing in the beginning Version conflicts and new documentation Subsequent latest updates and versions have caused chaos and confusion Here is a quick analysis of how the popularity of React has increased in recent years: Image SourceReact Prerequisites: Before diving into the learning path, you should have the following prerequisites Familiarity with any programming language Basic string, array manipulation operations OOPs concepts Basics of HTML, CSS, and JavaScript Deep interest to learn new skills Approach to master a skill:  These are the things you must consider while mastering a skill: Know your abilities, self-evaluate Track your learning process Create timelines Revise and focus on weak areas Take help from experts Practically apply whatever you have learnt so far Learn, do not cram Practice, practice and again, practice! Create projects Share your learning outcomes on LinkedIn, push your codes on GitHub repositories Compete online Online learning process: Learning new skills online saves a lot of time. We can learn at our own convenience and manage our schedules comfortably. While learning online: Choose a course based on values and outcomes It should include projects and technical support while learning A course that offers a mini-certification or a minor degree is more valuable Create a dedicated time-duration for your online classes Stick with the time and practice daily Focus on the main concepts and clear your doubts at the same time Maintain notes and revise them Ask good questions and get your doubts cleared. Here are a few courses you might wish to explore: Free:CodecademyEggheadEggheadScrimbaui.Dev Paid:EggheadFrontendmastersReacttrainingNewlineReact for beginnersYou can find other useful resources here.Roadmaps to learn React 1. Learn the basics of HTML: HTML stands for Hypertext Markup Language, and is a standard markup language to create web pages. We use different tags to structure the parts of a web page. Different HTML elements tell the browser how the content should be displayed on the browser. You must be aware of the following things: Basics of all tags, new features, and support in HTML5 How to link external CSS file Various attributes Embedding Audio, Images and Videos (Media) CSS: CSS stands for Cascading Style Sheets. It is used to format the web pages and primarily focuses on the look and feel of the web pages. We can control the styles of the HTML elements with CSS. We can also change the position, layout, arrangements of the HTML elements using CSS. We can add CSS to a HTML document in three ways – Inline, Internal and External.  Be sure to check-out the following points:  How to link external CSS files Attribute selectors Box-model JavaScript: It adds interactivity and dynamics in the HTML document. It is a client-side scripting language. To take inputs from users, validate them, display alerts etc., we use JavaScript.  Following are the important points to consider: Functions Strings Array manipulation Loops Printing alerts Logging on consoles2. Tools and Software GitHub: It is a hosting service which allows users to store and manage their source codes. It provides a helpful graphical UI (User Interface) to manage your projects. We can also access this using the command line. Once you start the actual coding and working on projects, you must use GitHub to manage your source codes. It also provides team collaboration. Focus on the following important points and learn: How to create a repository Pushing your code on GitHub Creating branches Git commands Team collaboration Version control Code Editors VS Code: It is a powerful source code editor used by most of the developers. It provides additional extensions and development tools which prove to be extremely helpful while writing the code.  3. Package Managers Npm or Yarn These are tools used to manage the packages and libraries. You can choose the package manager of your choice. Learn command line commands to create a project,  to install, remove - new modules, packages to update the versions 4. Advanced Concepts in Development ES6: It stands for ECMAScript 6, with ES6 being the 6th version of ECMAScript. ECMAScript was introduced to standardize JavaScript and was published in 2015. Due to new releases, there are some functionality changes in the previous concepts of React. State managements: It is a special technique which React uses to manipulate, update the values and data associated with the components. Passing values among components: Usually we pass the data from parent to child using props. There are alternative ways to pass the data using Redux and Context API. These are some advanced concepts which are particularly important. Component State/Context API Redux  Async and Await API Requests Promises Observable Helpers Data persistence 5. Better Styling using third party packages and plugins Learn how to add Bootstrap in your applications make your webpage responsive as per the various screen sizes apply Material Designs in your components, set default colors for your projects - Color palettes: primary, secondary, tertiary colors 6. Working with API Fetching data from APIs Get and Post requests Handling promises and observables 7. Routing and Navigation Loading other components in the same page Navigation among various components and views 8. Testing Testing is an important part in a Software Development Life Cycle. Testing ensures the quality of the development work. We use the following resources to test the React components. Jest: Jest is a JavaScript test runner that lets you access the DOM through jsdom.  React Testing Library: it is a lightweight solution to test the React components.  Find the official documentation here. Fundamentals Styling standards Create reusable and standard components and apply proper styling in components. Coding Standards Write reusable and quality code – writing a superior quality code enhances the performance of the whole application. Apply proper naming conventions while writing the code. Why should I learn React? Good community support Distinguished career ahead Regular updates and new versions Immense popularity Good income High demands in market Choice of new developers According to average salary of the React developer is: Challenges while learning As is the case when you are learning something new, you may find some challenges or difficulty in the learning process. You can take help from several communities, e.g., stackoverflow, quora etc. to clear your doubts. Focus on learning the following topics: Hooks and Redux Promises Data binding Functional and class-based components Lifecycle of components ConclusionTechnologies are changing at warp speed, and new innovations in the existing structures and workflow are implemented on a regular basis. To adapt to these changes, it's important to keep your skills and competencies updated as well. As some concepts and their implementations may be older,  always follow the official documentation, upskill yourself and stay relevant in the workforce!   

How to Learn React in 2022

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How to Learn React in 2022

One of the biggest challenges that all front-end developers face is building responsive and complex UI, while retaining high load time and enhancing performancesThe User Interface is what grabs the attention of the users and increases the popularity of your websiteA website that is slow and takes a lot of time to get loaded will be abandoned more often than notIn this respect React is a bestselling tool for developers, as it ensures better user experience and optimizes app performances.  

Though it sounds very cool, learning a new technology can be a daunting prospectA planned approach can be extremely helpful while learning new skills. 

Before we start, let us look at what we will learn in this blog! 

  1. Introduction to React 
  2. React VS Other frameworks 
  3. React prerequisites 
  4. Approach to mastering a skill 
  5. Online learning process 
  6. Roadmaps to learn React 
  7. Fundamentals 
  8. Why should I learn React? 
  9. Challenges while learning 
  10. Conclusion

Introduction to React: 

React is a powerful JavaScript Library, created by Facebook. It is open source and component-based UI library tool. 

How to Learn React in 2020

All the elements which we see in a website built on React are composed of several sub-components e.g., the buttons, side menus, navigation bar, headers, footers, paragraphs etc. 

To know about more about the components and other features you should check out this official documentation at.

React VS other Frameworks/Libraries 

The frameworks for Web development are: 

  • Angular 

Angular is an application design framework (not a JS Library) which is based on TypeScript and is open sourceIt is maintained and managed by the Angular Team at Google and can be used to create efficient Single Page Applications (SPAs) for enterprises. 

AngularPros: 

  1. Easily create Single Page Applications 
  2. Prototyping, Development, and testing becomes faster 
  3. It supports 2-way data binding 
  4. DOM Manipulation is easy and hence server-side load is minimized 
  5. Responsive web designing 
  6. Latest Angular versions support TypeScript which makes it easier to learn 
  7. Good community support 

Cons: 

  1. Challenging to understand MVC for beginners 
  2. Some features are difficult to understand e.g., dependency injection, services etc. 
  3. Poor response during Search Engine Optimization 

Official Documentation Link. 

  • Vuejs 

It is JavaScript-based UI framework. It is used for building user interfaces and creating Single Page Applications with the help of some libraries. 

VuejsPros: 

  1. Remarkably simple to use 
  2. It has good documentation 
  3. It supports virtual DOM Manipulation and 2-way Data binding 
  4. Unit testing can be efficiently done 
  5. Good community support 

Cons: 

  1. It is not suitable for large-scale projects 
  2. Limited resources 
  3. Not immensely popular among developers 

Official Documentation Link.

There are several other JS libraries and frameworks in the marketClick the links below to know more about these libraries or frameworks. 

How to Learn React in 2020

  • jQuery 

Official Documentation Link. 

  • Emberjs 

Official Documentation Link.

  • Backbonejs 

Official Documentation Link.

  • Semantic-UI 

Official Documentation Link.

  • Foundation 

Official Documentation Link.

  • Svelte 

Official Documentation Link.

Here’s what makes React more powerful than others: 

  1. It is based on Componentsand the same components can be reused 
  2. We can break the whole UI into smallest components 
  3. It is simple to use 
  4. One-way data binding 
  5. It uses virtual DOM, that means there is lesser load in the server-side rendering 
  6. High performance 
  7. Good documentation 

Downsides of React 

  1. JSX is very confusing in the beginning 
  2. Version conflicts and new documentation 
  3. Subsequent latest updates and versions have caused chaos and confusion 

Here is a quick analysis of how the popularity of React has increased in recent years: 

How to Learn React in 2020Image Source

React Prerequisites: 

Before diving into the learning path, you should have the following prerequisites 

  1. Familiarity with any programming language 
  2. Basic string, array manipulation operations 
  3. OOPs concepts 
  4. Basics of HTML, CSS, and JavaScript 
  5. Deep interest to learn new skills 

Approach to master a skill: 

 These are the things you must consider while mastering a skill: 

  1. Know your abilities, self-evaluate 
  2. Track your learning process 
  3. Create timelines 
  4. Revise and focus on weak areas 
  5. Take help from experts 
  6. Practically apply whatever you have learnt so far 
  7. Learn, do not cram 
  8. Practice, practice and again, practice! 
  9. Create projects 
  10. Share your learning outcomes on LinkedIn, push your codes on GitHub repositories 
  11. Compete online 

Online learning process: 

Learning new skills online saves lot of time. We can learn at our own convenience and manage our schedules comfortablyWhile learning online: 

  1. Choose a course based on values and outcomes 
  2. It should include projects and technical support while learning 
  3. A course that offers mini-certification or a minor degree is more valuable 
  4. Create a dedicated time-duration for your online classes 
  5. Stick with the time and practice daily 
  6. Focus on the main concepts and clear your doubts at the same time 
  7. Maintain notes and revise them 
  8. Ask good questions and get your doubts cleared. 

Here are a few courses you might wish to explore: 

Free:

  1. Codecademy
  2. Egghead
  3. Egghead
  4. Scrimba
  5. ui.Dev 

Paid:

  1. Egghead
  2. Frontendmasters
  3. Reacttraining
  4. Newline
  5. React for beginners

You can find other useful resources here.

Roadmaps to learn React 

1. Learn the basics of 

How to Learn React in 2020

  • HTMLHTML stands for Hypertext Markup Language, and is a standard markup language to create web pages. We use different tags to structure the parts of a web page. Different HTML elements tell the browser how the content should be displayed on the browser. 

You must be aware of the following things: 

  1. Basics of all tags, new features, and support in HTML5 
  2. How to link external CSS file 
  3. Various attributes 
  4. Embedding Audio, Images and Videos (Media) 
  • CSS: CSS stands for Cascading Style Sheets. It is used to format the web pages and primarily focuses on the look and feel of the web pages. We can control the styles of the HTML elements with CSS. We can also change the position, layout, arrangements of the HTML elements using CSS. 

We can add CSS to a HTML document in three ways – Inline, Internal and External.  

Be sure to check-out the following points:  

  1. How to link external CSS files 
  2. Attribute selectors 
  3. Box-model 
  • JavaScript: It adds interactivity and dynamics in the HTML document. It is client-side scripting language. To take inputs from users, validate them, display alerts etc., we use JavaScript.  

Following are the important points to consider: 

  1. Functions 
  2. Strings 
  3. Array manipulation 
  4. Loops 
  5. Printing alerts 
  6. Logging on consoles

2. Tools and Software 

  • GitHub: It is hosting service which allows users to store and manage their source codes. It provides a helpful graphical UI (User Interface) to manage your projects. We can also access this using the command line. Once you start the actual coding and working on projects, you must use GitHub to manage your source codes. It also provides team collaboration. 

Github

Focus on the following important points and learn: 

  1. How to create a repository 
  2. Pushing your code on GitHub 
  3. Creating branches 
  4. Git commands 
  5. Team collaboration 
  6. Version control 
  • Code Editors 

Visual Studio Code

VS CodeIt is a powerful source code editor used by most of the developers. It provides additional extensions and development tools which prove to be extremely helpful while writing the code.  

3. Package Managers 

Npm or Yarn 

These are tools used to manage the packages and libraries. You can choose the package manager of your choice. 

Learn command line commands to 

  1. create project 
  2. to install, remove - new modules, packages 
  3. to update the versions 

4. Advanced Concepts in Development 

ES6: It stands for ECMAScript 6, with ES6 being the 6th version of ECMAScript. ECMAScript was introduced to standardize JavaScript and was published in 2015. Due to new releases, there are some functionality changes in the previous concepts of React. 

  • State managements: It is a special technique which React uses to manipulate, update the values and data associated with the components. 
  • Passing values among components: Usually we pass the data from parent to child using props. There are alternative ways to pass the data using Redux and Context API. 

These are some advanced concepts which are particularly important. 

  • Component State/Context API 
  • Redux  
  • Async and Await 
  • API Requests 
  • Promises 
  • Observable 
  • Helpers 
  • Data persistence 

5. Better Styling using third party packages and plugins 

Learn how to 

  1. add Bootstrap in your applications 
  2. make your webpage responsive as per the various screen sizes 
  3. apply Material Designs in your components, 
  4. set default colors for your projects - Color palettes: primary, secondary, tertiary colors 

Bootstrap

6. Working with API 

  • Fetching data from APIs 
  • Get and Post requests 
  • Handling promises and observables 

How to Learn React in 2020

7. Routing and Navigation 

  • Loading other components in the same page 
  • Navigation among various components and views 

8. Testing 

Testing is an important part in a Software Development Life Cycle. Testing ensures the quality of the development work. We use the following resources to test the React components. 

  • Jest: Jest is a JavaScript test runner that lets you access the DOM through jsdom 
  • React Testing Library: it is a lightweight solution to test the React components.  

Find the official documentation here. 

Fundamentals 

  • Styling standards 

Create reusable and standard components and apply proper styling in components. 

  • Coding Standards 

  1. Write reusable and quality code – writing a superior quality code enhances the performance of the whole application. 

  1. Apply proper naming conventions while writing the code. 

Why should I learn React? 

  • Good community support 
  • Distinguished career ahead 
  • Regular updates and new versions 
  • Immense popularity 
  • Good income 
  • High demands in market 
  • Choice of new developers 

According to average salary of the React developer is

How to Learn React in 2020

How to Learn React in 2020

Challenges while learning 

As is the case when you are learning something new, you may find some challenges or difficulty in the learning process. You can take help from several communities, e.g., stackoverflowquora etc. to clear your doubts. Focus on learning the following topics: 

  • Hooks and Redux 
  • Promises 
  • Data binding 
  • Functional and class-based components 
  • Lifecycle of components 

Conclusion

Technologies are changing at warp speed, and new innovations in the existing structures and workflow are implemented on a regular basis. To adapt to these changesit's important to keep your skills and competencies updated as well. As some concepts and their implementations may be older,  always follow the official documentation, upskill yourself and stay relevant in the workforce  

KnowledgeHut

KnowledgeHut

Author

KnowledgeHut is an outcome-focused global ed-tech company. We help organizations and professionals unlock excellence through skills development. We offer training solutions under the people and process, data science, full-stack development, cybersecurity, future technologies and digital transformation verticals.
Website : https://www.knowledgehut.com

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Handling React Events - A Detailed Guide

Event handling essentially allows the user to interact with a webpage and do something specific when a certain event like a click or a hover happens. When the user interacts with the application, events are fired, for example, mouseover, key press, change event, and so on. The application must handle events and execute the code. In short, events are the actions to which javascript can respond.   The actions to which javascript can respond are called events. Handling events with react is  very similar to handling events in DOM elements. Below are some general events that you would see in and out when dealing with react based websites:  Clicking an element  Submitting a form Scrolling page Hovering an element  Loading a webpage Input field change User stroking a key Image loading Naming Events in React Handling events with react is very similar to handling events in DOM elements, although there are some syntactic differences.   React events are written in camelCase.   A function is passed as the event handler rather than string. The way to write events in html / DOM is below:        click me onclick is written in lower case in html as shown above and what action to take when this onclick event triggers is taken care of by handleClick.In React, events are named using camel case and you pass a function as event handler as shown below:  Like in a functional component, event is written like below:       click me   In class based component ,event is written like below        click me Defining Events:Events are normally used in combination with functions, and the function is not executed until the event occurs, and the combination of event, HTML element, and javascript function is called binding which means to map all three. Generic syntax is:      Example:  Create a button element and what happens when onClick event triggered is driven by the function which is func() shown below     click me Let’s see some of the event attributes:   onmouseover : The mouse is moved over an element onmouseup : The mouse button is released onmouseout : The mouse  is moved off an element onmousemove: The mouse is moved Onmousedown: mouse button is pressed  onload : A image is done loading onunload: Existing the page  onblur : Losing Focus  on element  onchange : Content of a field changes onclick: Clicking an object  ondblclick: double clicking an object  onfocus element getting a focus  Onkeydown: pushing a keyboard key Onkeyup: keyboard key is released Onkeypress: keyboard key is pressed  Onselect: text is selected These are some examples of events:                                         Events                               function testApp (){                        alert((“Hello Event”);                                                   test Clicked                  test double Clicked                     Synthetic Events When you specify an event in JSX, you are not directly dealing with regular DOM events, you are dealing with a react event type called a synthetic event.It's a simple wrapper for native event instances and every synthetic event created needs to be garbage-collected which can be resource intensive in terms of CPU. The synthetic event object has properties mentioned below:  Boolean isTrusted  DOMEvent nativeEvent number timeStamp   void preventDefault() number eventPhase Synthetic events provide an interface and reduce browser inconsistencies and the event contains required information for its propagation to work. Synthetic event is reused for performance reasons in the browser, A synthetic event is a cross-browser wrapper around the browser’s native event it has the same interface as the native event. Synthetic events are delegated to the document node. Therefore native events are triggered first and the events bubble up to document, after which the synthetic events are triggered. The synthetic event object will be reused and all the properties will be nullified after the event callback has been invoked and this is for performance reasons.The workflow of synthetic event in react is:    Element ---- > Event ---- > synthetic event  ---- > handler(e)                                |                                                      |                                |  _______  Component ________|  umber timeStamp The Basics of React Event Handling Let’s explore how to handle events in react and we will showcase the click event and how it holds good for other types of events. Let’s start with functional components by creating a  file as clickAppHandler.js.In this file let’s create a  functional component  as shown below                        Import React from ‘...react’                         function clickAppHandler() {                                function clickHandler() {                                        console.log(‘clicked’)                                         }                                  return (                                                                                  Click                                                                          )                         }                       export default clickAppHandler  When onClick event triggers clickHandler function is called as shown below and when you click the button console will print the string “clicked” After this you need the add a component in the app component. In our code above you can see on click we pass the function as event handler and you will notice that we haven't added parentheses as it becomes a function, and we do not want that and we want handler to be a function not a function call. When a new component is rendered its event handler functions are added to the mapping maintained by the react.When the event is triggered and it hits and DOM object ,react maps the event to the handler, if it matches it calls the handler. The event handling in react is declarative and the advantage of declarative way to handlers is that they are part of the User interface structure.  Let’s take a look at event handling in class components                       Import React, { Component } from ‘...react’                         class TestApp extends Component {                              clickHandler() {                                  console.log(“clicked”)                                }                                render(){                                      return(                                                                                     Click me                                                                                 )                                 }                            }                       export default TestApp You cannot return false to prevent default behaviour in React. You must call preventDefault explicitly.  In HTML it looks like below:    Click Output: It will print “Clicked”  And in React, like this:  function clickHandle(e) {       e.preventDefault();       console.log(“Handled”);   }  Click  Output : console will print “Handled”  There are some  event handlers triggered by an event in the bubbling phase which is the same as with the normal DOM API; simply attach a handler to an eventual parent of an element and any events triggered on that element will bubble to the parent as long as it's not stopped via stopPropagation along the way   Click me  Below are some of the event handlers triggered in the bubbling phase:  MouseEvents           onClick           onDrag          onDoubleClick Keyboard Events                    onKeyDown                    onKeyPress                    onKeyUp Focus Events                  onFocus   onBlur To capture an event handler for the capture phase, append capture to the event name. For example, instead of using onClick, use onClickCapture to handle the click event.  Capture event example:                  Click me    Additional ExamplesExample1                       Import React from ‘...react’                         function clickAppHandler() {                                function clickHandler() {                                        console.log(‘clicked’)                                         }                                  return (                                                                                  Click                                                                          )                         }                       export default clickAppHandler   Example2       This example is along with HTML in a single file                                                            Events                               function testApp (){                        alert((“Hello Event”);                                                   test Clicked                  test double Clicked                     Adding Events: Below example is how you add an event. Highlighted in bold                      Import React from ‘...react’                         function clickAppHandler() {                                function clickHandler() {                                        console.log(‘clicked’)                                         }                                  return (                                                                                  Click                                                                          )                         }                       export default clickAppHandler  Passing Arguments to Event HandlerThere are two ways arguments are passed to event handler  Arrow function                    this.handleClick(id,e)}>Click                onClick is the event                e is the event object                 id can be state or props or some data Bind method      Click  In this case event object is automatically passed In both methods e represents the react event and its passed after the ID as second argument,With an arrow function this event e is passed explicitly but with bind method its automatically passed.                                     Import React,{ Component } from “react”;                                         class TestApp extends Component {                                           state = {                                                       id: 2,                                                      Name: “TestApp Dummy”                                                };                                                             //arrow function                                                 handleClick = (id,e) => {                                                       console.log(id);                                                       console.log(e);                                                  };                                               handleArg = (e) => { this.handleClick(this.state.id,e);}                                                          render() {     return (                    TestApp,{this.state.name}            onClick={this.handleArg}>Display            );   }  }  The react event is an object and obtained from react. Instead of creating a separate function for passing argument, you can directly pass the anonymous arrow function as shown in the render function below:     render() {        return (                                                                                                       TestApp,{this.state.name}                                                {                           this.handleClick(this.state.id,e);                                                               }}>Display                                                                                                         );                                                 }                                            }    Output:   click on button  “TestApp Dummy “                   Let’s see only how bind method looks like in the render function    render() {                                         return (                                                                                                 TestApp,{this.state.name}                                                   Display                                                                                                       );                                                  }                                              } Output: this will display the h1 tag and when you click the button handleClick function gets invoked and the console will display id of the state object as shown above. Building a Practice to Thoroughly Understand Events This blog focuses on event handling, which in turn teaches about event handlers declared in JSX markup.This approach helps in tracking down the element mapped with events in an easy way.  We also learned how to handle multiple event handlers in a single element by using JSX attributes.we also learned about ways to bind event handler and  parameter values. Then we learned about synthetic events which are abstractions around native events. The best way you can retain this learning is by practicing more and tackling the complexities that may arise as you practice. You can find several tutorials on the internet or share your questions with us here. Happy learning! 
5355
Handling React Events - A Detailed Guide

Event handling essentially allows the user to inte... Read More

MongoDB Query Document Using Find() With Example

MongoDB's find() method selects documents from a collection or view and returns a cursor to those documents. There are two parameters in this formula: query and projection.Query – This is an optional parameter that specifies the criteria for selection. In simple terms, a query is what you want to search for within a collection.Projection – This is an optional parameter that specifies what should be returned if the query criteria are satisfied. In simple terms, it is a type of decision-making that is based on a set of criteria.MongoDB's Flexible SchemaA NoSQL database, which stands for "not only SQL," is a way of storing and retrieving data that is different from relational databases' traditional table structures (RDBMS).When storing large amounts of unstructured data with changing schemas, NoSQL databases are indeed a better option than RDBMS. Horizontal scaling properties of NoSQL databases allow them to store and process large amounts of data.These are intended for storing, retrieving, and managing document-oriented data, which is frequently stored in JSON format (JavaScript Object Notation). Document databases, unlike RDBMSs, have a flexible schema that is defined by the contents of the documents.MongoDB is one of the most widely used open-source NoSQL document databases. MongoDB is known as a 'schemaless' database because it does not impose a specific structure on documents in a collection.MongoDB is compatible with a number of popular programming languages. It also offers a high level of operational flexibility because it scales well horizontally, allowing data to be spread or 'sharded' across multiple commodity servers with the ability to add more servers as needed. MongoDB can be run on a variety of platforms, including developer laptops, private clouds, and public clouds.Querying documents using find()MongoDB queries are used to retrieve or fetch data from a MongoDB database. When running a query, you can use criteria or conditions to retrieve specific data from the database.The function db.collection is provided by MongoDB. find() is a function that retrieves documents from a MongoDB database.In MongoDB, the find method is used to retrieve a specific document from the MongoDB collection. In Mongo DB, there are a total of six methods for retrieving specific records.find()findAndModify()findOne()findOneAndDelete()findOneAndReplace()findOneAndUpdate()Syntax:find(query, projection)We can fetch a specific record using the Find method, which has two parameters. If these two parameters are omitted, the find method will return all of the documents in the MongoDB collection.Example:Consider an example of employees with the database of employee_id and employee_name and we will fetch the documents using find() method.First, create a database with the name “employees” with the following code:use employeesNow, create a collection “employee” with:db.createCollection("employee")In the next step we will insert the documents in the database:db.employee.insert([{employee_id: 101, employee_name: "Ishan"}, {employee_id: 102, employee_name: "Bhavesh"}, {employee_id: 103, employee_name: "Madan"}])Find all Documents:To get all the records in a collection, we need to use the find method with an empty parameter. In other words, when we need all the records, we will not use any parameters.db.employee.find()Output in Mongo ShellThe pretty() method can be used to display the results in a formatted manner.Syntax:db.COLLECTION_NAME.find().pretty()Let’s check our documents with pretty() method:Query FiltersWe will see examples of query operations using the db.collection.find() method in mongosh.We will use the employee collection in the employees database.db.employee.insert([{employee_id: 101, employee_name: "Ishan", age: 21, email_id: "ishanjain@gmail.com"}, {employee_id: 102, employee_name: "Bhavesh", age: 22, email_id: "bhaveshg@gmail.com"}, {employee_id: 103, employee_name: "Madan", age: 23, email_id: "madan@gmail.com"}])As we have seen earlier that to select all the documents in the database we pass an empty document as the query filter parameter to the find method.db.employee.find().pretty()Find the first document in a collection:db.employee.findOne()Find a document by ID:db.employee.findOne({_id : ObjectId("61d1ae0b56b92c20b423a5a7")})Find Documents that Match Query Criteriadb.employee.find({“age”: “22”})db.employee.find({"employee_name": "Madan"}).pretty()Sort Results by a Field:db.employee.find().sort({age: 1}).pretty()order by age, in ascending orderdb.employee.find().sort({age: -1}).pretty()order by age, in descending orderAND Conditions:A compound query can specify conditions for multiple fields in the documents in a collection. A logical AND conjunction connects the clauses of a compound query indirectly, allowing the query to select all documents in the collection that meet the specified conditions.In the following example, we will consider all the documents in the employee collection where employee_id equals 101 and age equals 21.db.employee.find({"employee_id": 101, "age": "21" }).pretty()Querying nested fieldsThe embedded or nested document feature in MongoDB is a useful feature. Embedded documents, also known as nested documents, are documents that contain other documents.You can simply embed a document inside another document in MongoDB. Documents are defined in the mongo shell using curly braces (), and field-value pairs are contained within these curly braces.Using curly braces, we can now embed or set another document inside these fields, which can include field-value pairs or another sub-document.Syntax:{ field: { field1: value1, field2: value2 } }Example:We have a database “nested” and in this database we have collection “nesteddoc”.The following documents will insert into the nesteddoc collection.db.nesteddoc.insertMany([ { "_id" : 1, "dept" : "A", "item" : { "sku" : "101", "color" : "red" }, "sizes" : [ "S", "M" ] }, { "_id" : 2, "dept" : "A", "item" : { "sku" : "102", "color" : "blue" }, "sizes" : [ "M", "L" ] }, { "_id" : 3, "dept" : "B", "item" : { "sku" : "103", "color" : "blue" }, "sizes" : "S" }, { "_id" : 4, "dept" : "A", "item" : { "sku" : "104", "color" : "black" }, "sizes" : [ "S" ] } ])Place the documents in the collection now. Also, take a look at the results:As a result, the nesteddoc collection contains four documents, each of which contains nested documents. The find() method can be used to access the collection's documents.db.nesteddoc.find()Specify Equality Condition:In this example, we will select the document from the nesteddoc query where dept equals “A”.db.nesteddoc.find({dept: "A"})Querying ArraysUse the query document {: } to specify an equality condition on an array, where is the exact array to match, including the order of the elements.The following query looks for all documents where the field tags value is an array with exactly two elements, "S" and "M," in the order specified:db.nesteddoc.find( { sizes: ["S", "M"] } )Use the $all operator to find an array that contains both the elements "S" and "M," regardless of order or other elements in the array:db.nested.find( { sizes: { $all: ["S", "M"] } } )Query an Array for an Element:The following example queries for all documents where size is an array that contains the string “S” as one of its elements:db.nesteddoc.find( { sizes: "S" } )Filter conditionsTo discuss the filter conditions, we will consider a situation that elaborates this. We will start by creating a collection with the name “products” and then add the documents to it.db.products.insertMany([ { _id: 1, item: { name: "ab", code: "123" }, qty: 15, tags: [ "A", "B", "C" ] }, { _id: 2, item: { name: "cd", code: "123" }, qty: 20, tags: [ "B" ] }, { _id: 3, item: { name: "ij", code: "456" }, qty: 25, tags: [ "A", "B" ] }, { _id: 4, item: { name: "xy", code: "456" }, qty: 30, tags: [ "B", "A" ] }, { _id: 5, item: { name: "mn", code: "000" }, qty: 20, tags: [ [ "A", "B" ], "C" ] }])To check the documents, use db.products.find():$gt$gt selects documents with a field value greater than (or equal to) the specified value.db.products.find( { qty: { $gt: “20” } } )$gte:$gte finds documents in which a field's value is greater than or equal to (i.e. >=) a specified value (e.g. value.)db.products.find( { qty: { $gte: 20 } } )$lt:$lt selects documents whose field value is less than (or equal to) the specified value.db.products.find( { qty: { $lt: 25 } } )$lte:$lte selects documents in which the field's value is less than or equal to (i.e. =) the specified value.db.products.find( { qty: { $lte: 20 } } )Query an Array by Array Length:To find arrays with a specific number of elements, use the $size operator. For example, the following selects documents with two elements in the array.db.products.find( { "tags": {$size: 2} } )ProjectionIn MongoDB, projection refers to selecting only the data that is required rather than the entire document's data. If a document has five fields and you only want to show three of them, select only three of them.The find() method in MongoDB accepts a second optional parameter, which is a list of fields to retrieve, as explained in MongoDB Query Document. When you use the find() method in MongoDB, it displays all of a document's fields. To prevent this, create a list of fields with the values 1 or 0. The value 1 indicates that the field should be visible, while 0 indicates that it should be hidden.Syntax:db.COLLECTION_NAME.find({},{KEY:1})Example:We will consider the previous example of products collection. Run the below command on mongoshell to learn how projection works:db.products.find({},{"tags":1, _id:0})Keep in mind that the _id field is always displayed while executing the find() method; if you do not want this field to be displayed, set it to 0.Optimized FindingsTo retrieve a document from a MongoDB collection, use the Find method.Using the Find method, we can retrieve specific documents as well as the fields that we require. Other find methods can also be used to retrieve specific documents based on our needs.By inserting array elements into the query, we can retrieve specific elements or documents. To retrieve data for array elements from the collection in MongoDB, we can use multiple query operators.
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MongoDB Query Document Using Find() With Example

MongoDB's find() method selects documents from a c... Read More

Implementing MongoDb Map Reduce using Aggregation

Algorithms and applications in today's data-driven market collect data about people, processes, systems, and organisations 24 hours a day, seven days a week, resulting in massive amounts of data. The problem is figuring out how to process this massive amount of data efficiently without sacrificing valuable insights.What is Map Reduce? The MapReduce programming model comes to the rescue here. MapReduce, which was first used by Google to analyse its search results, has grown in popularity due to its ability to split and process terabytes of data in parallel, generating results faster. A (Key,value) pair is the basic unit of information in MapReduce. Before feeding the data to the MapReduce model, all types of structured and unstructured data must be translated to this basic unit. The MapReduce model, as the name implies, consists of two distinct routines: the Map-function and the Reduce-function.  MapReduce is a framework for handling parallelizable problems across huge files using a huge number of devices (nodes), which are collectively referred to as a cluster (if all nodes are on the same local network and use similar hardware) or a grid (if the nodes are shared across geographically and administratively distributed systems, and use more heterogeneous hardware).  When data stored in a filesystem (unstructured) or a database(structured) is processed, MapReduce can take advantage of data's locality, processing it close to where it's stored to reduce communication costs. Typically, a MapReduce framework (or system) consists of three operations: Map: Each worker node applies the map function to local data and saves the result to a temporary storage. Only one copy of the redundant input data is processed by a master node. Shuffle: worker nodes redistribute data based on output keys (produced by the map function), ensuring that all data associated with a single key is stored on the same worker node. Reduce: each group of output data is now processed in parallel by worker nodes, per key. This article will walk you through the Map-Reduce model's functionality step by step. Map Reduce in MongoDB The map-reduce operation has been deprecated since MongoDB 5.0. An aggregation pipeline outperforms a map-reduce operation in terms of performance and usability. Aggregation pipeline operators like $group, $merge, and others can be used to rewrite map-reduce operations. Starting with version 4.4, MongoDB provides the $accumulator and $function aggregation operators for map-reduce operations that require custom functionality. In JavaScript, use these operators to create custom aggregation expressions. The map and reduce functions are the two main functions here. As a result, the data is independently mapped and reduced in different spaces before being combined in the function and saved to the specified new collection. This mapReduce() function was designed to work with large data sets only. You can perform aggregation operations like max and avg on data using Map Reduce, which is similar to groupBy in SQL. It works independently and in parallel on data. Implementing Map Reduce with Mongosh (MongoDB Shell)  The db.collection.mapReduce() method in mongosh is a wrapper for the mapReduce command. The examples that follow make use of the db.collection.mapReduce(). Example: Create a collection ‘orders’ with these documents: db.orders.insertMany([     { _id: 1, cust_id: "Ishan Jain", ord_date: new Date("2021-11-01"), price: 25, items: [ { sku: "oranges", qty: 5, price: 2.5 }, { sku: "apples", qty: 5, price: 2.5 } ], status: "A" },     { _id: 2, cust_id: "Ishan Jain", ord_date: new Date("2021-11-08"), price: 70, items: [ { sku: "oranges", qty: 8, price: 2.5 }, { sku: "chocolates", qty: 5, price: 10 } ], status: "A" },     { _id: 3, cust_id: "Bhavesh Galav", ord_date: new Date("2021-11-08"), price: 50, items: [ { sku: "oranges", qty: 10, price: 2.5 }, { sku: "pears", qty: 10, price: 2.5 } ], status: "A" },     { _id: 4, cust_id: "Bhavesh Galav", ord_date: new Date("2021-11-18"), price: 25, items: [ { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" },     { _id: 5, cust_id: "Bhavesh Galav", ord_date: new Date("2021-11-19"), price: 50, items: [ { sku: "chocolates", qty: 5, price: 10 } ], status: "A"},     { _id: 6, cust_id: "Madan Parmar", ord_date: new Date("2021-11-19"), price: 35, items: [ { sku: "carrots", qty: 10, price: 1.0 }, { sku: "apples", qty: 10, price: 2.5 } ], status: "A" },     { _id: 7, cust_id: "Madan Parmar", ord_date: new Date("2021-11-20"), price: 25, items: [ { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" },     { _id: 8, cust_id: "Abhresh", ord_date: new Date("2021-11-20"), price: 75, items: [ { sku: "chocolates", qty: 5, price: 10 }, { sku: "apples", qty: 10, price: 2.5 } ], status: "A" },     { _id: 9, cust_id: "Abhresh", ord_date: new Date("2021-11-20"), price: 55, items: [ { sku: "carrots", qty: 5, price: 1.0 }, { sku: "apples", qty: 10, price: 2.5 }, { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" },     { _id: 10, cust_id: "Abhresh", ord_date: new Date("2021-11-23"), price: 25, items: [ { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" }  ]) Apply a map-reduce operation to the orders collection to group them by cust_id, then add the prices for each cust_id: To process each input document, define the map function: this refers the document that the map-reduce operation is processing in the function. For each document, the function maps the price to the cust_id and outputs the cust_id and price. var mapFunction1 = function() {emit(this.cust_id, this.price);}; With the two arguments keyCustId and valuesPrices, define the corresponding reduce function: The elements of the valuesPrices array are the price values emitted by the map function, grouped by keyCustId. The valuesPrice array is reduced to the sum of its elements by this function. var reduceFunction1 = function(keyCustId, valuesPrices) {return Array.sum(valuesPrices);};Apply the mapFunction1 map function and the reduceFunction1 reduce function to all documents in the orders collection: db.orders.mapReduce(mapFunction1,reduceFunction1,{ out: "map_reduce_example" }) The results of this operation are saved in the map_reduce_example collection. If the map_reduce_example collection already exists, the operation will overwrite its contents with the map-reduce operation's results. Check the map_reduce_example collection to verify: db.map_reduce_example.find().sort( { _id: 1 } ) Aggregation Alternative:You can rewrite the map-reduce operation without defining custom functions by using the available aggregation pipeline operators: db.orders.aggregate([{$group: { _id:"$cust_id",value:{$sum: "$price" } } },{ $out: "agg_alternative_1" }]) Check the agg_alternative_1 collection to verify: db.agg_alternative_1.find().sort( { _id: 1 } )Implementing Map Reduce with Java Consider the collection car and insert the following documents in it. db.car.insert( [ {car_id:"c1",name:"Audi",color:"Black",cno:"H110",mfdcountry:"Germany",speed:72,price:11.25}, {car_id:"c2",name:"Polo",color:"White",cno:"H111",mfdcountry:"Japan",speed:65,price:8.5}, {car_id:"c3",name:"Alto",color:"Silver",cno:"H112",mfdcountry:"India",speed:53,price:4.5}, {car_id:"c4",name:"Santro",color:"Grey",cno:"H113",mfdcountry:"Sweden",speed:89,price:3.5} , {car_id:"c5",name:"Zen",color:"Blue",cno:"H114",mfdcountry:"Denmark",speed:94,price:6.5} ] ) You will get an output like this:  Let's now write the map reduce function on a collection of cars, grouping them by speed and classifying them as overspeed cars.  var speedmap = function (){  var criteria;  if ( this.speed > 70 ) {criteria = 'overspeed';emit(criteria,this.speed);}}; Based on the speed, this function classifies the vehicle as an overspeed vehicle. The term "this" refers to the current document that requires map reduction. var avgspeed_reducemap = function(key, speed) {       var total =0;       for (var i = 0; i 
7344
Implementing MongoDb Map Reduce using Aggregation

Algorithms and applications in today's data-driven... Read More