What Is React JS? | React JS Tutorial for Beginners

What is React JS?

In simple terms, it is a JavaScript library for building user interfaces. Before we deep dive into the rest of the React JS tutorial, let us understand the basic concepts. In this definition, we see two words: javascript library and user interface. Let’s understand what these terms mean. 

The library is a pre-written code that is efficient, complex, composed, and readily available. Thus, it makes our life easy, and we can easily use the code written by someone else. 

Let’s say we want to calculate the cosine value of 20. Rather than worrying about how this library has been written, we simply use the math library. For example, Math.cos(20).

User Interface refers to what the user sees upfront.

React JS is a very powerful tool that enables efficient front-end development by breaking up the page into several building blocks known as components.

Also Read: How to choose the right programming language?

Prerequisites for React JS

Before we dive into the depths of our React JS Tutorial, there are certain prerequisites to keep in mind. We must have basic hands-on knowledge of HTML, CSS, and JavaScript as they are the foundation stones for any frontend development and are indispensable for becoming an expert.

1. HTML

• Stands for Hypertext Markup Language
• It is a markup language for creating web pages/documents
• Basic Tags:

<div> <span>: used to group elements.
<form>: to create a form that is responsible for fetching data from users.
<input>: specifies what and how the input should be taken from users.
<button>: creates a button and specifies its functionalities that will get executed once it is clicked.

2. CSS

• Stands for Cascading Style Sheet
• It is more responsible for the look and feel of the webpage.
• You can select elements from HTML and apply styling to it.
• General Syntax:

selector{
property1 : value1; 
property2 : value2; 
property3 : value3;
}

There are 3 major selectors in CSS:

• Id(#) – unique in a HTML doc
• Class(.) – group of elements 
• Tag(tag name) – all tags of the specific tag name

-Box Model

• Every element is treated as a rectangular box
• Each box comprises of 4 edges
• Content 
• Padding
• Margin 
• Border
• You also need a good understanding of other properties like colors, font, backgrounds, etc. 

3. JavaScript

1. Arrays
2. Objects
3. Functions
4. Control Flow Statements
5. DOM Manipulation
6. DOM Events
7. Closure
8. Prototype
9. OOPs

With this in mind, you can ensure that you clearly understand the rest of the React JS Tutorial.

Why use React JS?

Image Source: Google Trends

Now that you understand what React means, we can move to the next step of the React JS tutorial and understand why we use it.

React is a powerful and very popular tool in front-end development.

React is more popular than its competitors such as Vue and Angular. One of the main reasons for its popularity is that React is a Library. Thus, the control over the flow of the application is more when compared to Angular, which is a framework.

We can easily reuse the components which help in the optimization. The learning curve of React is very easy as compared to Angular and Vue. React is trusted by some of the leading companies like Facebook, Netflix, PayPal, Tesla, and more.
We see the real benefits of React when we build a single page application. There are more jobs in the market for React developers compared to Angular and Vue.

Single Page Application

In the traditional system, multiple server requests were sent with multiple reloading. This resulted in low performance, more bandwidth, it was more time-consuming. But with single-page applications, only a single request is made, and the server responds while loading data is re-written.

Everything on the web page is in the form of components. With the help of Virtual DOM, the component which is required to reload is found and updates that object in the actual DOM without reloading every component on the webpage.

Single Page Applications save time, bandwidth, and improve performance. Some SPA are Gmail, Facebook, and Twitter.

JSX

JSX – Stands for JavaScript XML

It is used by React to allow HTM code to co-exist with JavaScript code.

Traditionally, we used to incorporate JavaScript in HTML. But with JSX, you can now incorporate HTML in JavaScript.

Babel is the compiler used to transform JSX into React code. Take a look at the following example:

React Component

React allows you to divide your pages into independent building blocks that can be created, maintained, manipulated, reused independently, and then merged to construct the entire page.

Say you are visiting the above webpage. This webpage can be broken down into multiple components:

• Top green portion
• Circular image
• Description text under every image
• Location 
• Contact
• Email

Circular image and Description text are present four times on this page with the same skeleton but different content.

React can use this to its advantage by creating components once and then using it as per the requirement.

Two types of components React deals with:

• Functional Component
  • Contains only render function 
  • No state
  • Simple JS functions 
  • May take props as parameters and return the output to be rendered.
  • Example:
• Class-Based Component
  • In addition to render(), it also extends from React 
  • More complex and flexible but deprecated
  • Example of Class-Based component is given below:

State and Props in React JS 

State:

• State is defined and managed within a class whenever we extend components from React library
• State stores the components property values
• Components get re-rendered whenever the state gets modified

Props:

• Props refer to attributes of the components
• These attributes can be accessed in the component definition 
• In functional components to access content { object_name.attribute }
• In class based components to access content { this.attribute }

Also Read: Want to become a full-stack developer? Here’s how.

Virtual DOM

Let’s say you are in the process of constructing a house for a family.

After you complete the construction, if the family is not happy with it, you will start the construction from scratch. Now, when every new family visits, if they were not satisfied then the construction and deconstruction will continue. This is a very time-consuming process.

But let’s say that you first showed them the blueprint of the house and they asked for some changes. You updated it and then some more changes were requested.

This situation is much simpler because only the blueprint is going through the basic changes. Once finalized, the desired house can be constructed for the family. Leaving them with their dream home. This is what Virtual DOM does.

A copy of DOM is created and all the changes made are rewritten on this copy.

Finally, React only updates the difference of virtual DOM on original DOM.

Node JS and React JS

Setting up Local Development Server

1. Download and Install NodeJS 

2. Download and Install Any Editor

Create React App

Create React App was developed by Facebook and is an official way to create a single page application.

• It is the best practice to create single-page React applications.
• You don’t need to install or configure other tools for development.
• You also don’t require Webpack or Babel.
• Gives a head start thus saving a lot of time and pain.

Our First React App

We hope you’re enjoying the React JS tutorial so far. Let’s start our first React app development with the help of Create-React-App.

Step 1: Open the Node.js command prompt. 

Step 2: Run “npm install create-react-app -g” command on the terminal for windows (“sudo npm install create-react-app -g” for Mac) to install and create a react app globally.

Step 3: Navigate to the path where you want to create the folder using create-react-app.

Step 4: Run the create-react-app command along with the Project_Name. 

Step 5: Navigate to the project using “ cd  Project_Name” and run npm start command.

Next Generation JavaScript 

1. Let

It is responsible for declaring the variables block-scoped which was not in case of a “var” keyword.

The variables cannot be redeclared into var if written within the same block and if in different blocks, let variables can be redeclared.

Here is a written code snippet, the variable name has been redeclared but in different blocks, had it been in the same block would have resulted in an error.

2. Const

We can use const keywords to make var, function, or object constant. If an object is constant, you can’t reassign it but can manipulate its properties.

In this written code snippet, we have added the property name to the object, but if we tried to change the reference of the same object, it would have flagged the error.

3. Function declaration

It starts with a function keyword and it gets its definition at compile time. Follows the same standard of declaring the function and then calling it by its name. Here is a written code snippet showing us how to declare the function and how to call the function.

4. Function Expression

A variable that gets assigned with the function is used here. The function gets its definition at runtime. The name of the function wasn’t required here and the same function was called by the variable it was assigned to. This written code snippet shows us how to declare and call the function.

5. Arrow function in JavaScript

Shorthand for a function expression. If there is a single line in function, it will by default assume it to return. Arrow function removed the problems associated with the “this” keyword. In the arrow function, we don’t use bind operation. The written code snippet below shows us how to define arrow function with parameters.

6. Export

Export keyword helps us use one JavaScript file in another JavaScript file. The written code snippet below shows us how to export objects. When we use the default keyword, its syntax(left side) and without using the default keyword(right side).

7. Import

To include the exported file, we use the “Import” keyword in the destination JS file. The written code snippet shows how to import objects. When we use default keywords, its syntax(left side), and naming the object the same is not restricted, and without using the default keyword(right side) its syntax and naming of objects are restricted.

8. Spread

• A spread operator is used with arrays or objects
• A spread operator is used to retrieve all values or properties from one array/object into another
• Represented by three dots(…)
• Below written code snippet showing how to use the spread operator and its syntax.

9. Rest

• The rest operator is used with functions
• It forms an array of arguments passed to the function
• Rest is represented as (…)
• Below written code snippet showing how to use the rest operator and its syntax.

10. Destructuring

• Destructuring is a way with which we can extract a few elements from the array or few properties from the object which was not in the case of spread and rest operators.
• Below written code snippet showing how to use the destructuring operator and its syntax.

In conclusion, this is how you can get started with React. Found this React JS tutorial helpful? Stay tuned for more such tutorials.

Looking for a way to learn React JS for free? Check out these react js free courses. With these courses, you’ll be able to learn everything you need to know about React JS, including how to create amazing user interfaces and how to manage state.

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Original article source at: https://www.mygreatlearning.com

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How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

• Performance: It delivers optimal performance.
• Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
• UI design: React Native enables you to design simple and responsive UI for your mobile app.
• 3rd party plugins: This framework supports 3rd party plugins.
• Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

• Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
• Near-native user experience: React Native provides several native components, and these are platform agnostic.
• The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

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NBB: Ad-hoc CLJS Scripting on Node.js

Nbb

Not babashka. Node.js babashka!?

Ad-hoc CLJS scripting on Node.js.

Status

Experimental. Please report issues here.

Goals and features

Nbb's main goal is to make it easy to get started with ad hoc CLJS scripting on Node.js.

Additional goals and features are:

• Fast startup without relying on a custom version of Node.js.
• Small artifact (current size is around 1.2MB).
• First class macros.
• Support building small TUI apps using Reagent.
• Complement babashka with libraries from the Node.js ecosystem.

Requirements

Nbb requires Node.js v12 or newer.

How does this tool work?

CLJS code is evaluated through SCI, the same interpreter that powers babashka. Because SCI works with advanced compilation, the bundle size, especially when combined with other dependencies, is smaller than what you get with self-hosted CLJS. That makes startup faster. The trade-off is that execution is less performant and that only a subset of CLJS is available (e.g. no deftype, yet).

Usage

Install nbb from NPM:

$ npm install nbb -g

Omit -g for a local install.

Try out an expression:

$ nbb -e '(+ 1 2 3)'
6

And then install some other NPM libraries to use in the script. E.g.:

$ npm install csv-parse shelljs zx

Create a script which uses the NPM libraries:

(ns script
  (:require ["csv-parse/lib/sync$default" :as csv-parse]
            ["fs" :as fs]
            ["path" :as path]
            ["shelljs$default" :as sh]
            ["term-size$default" :as term-size]
            ["zx$default" :as zx]
            ["zx$fs" :as zxfs]
            [nbb.core :refer [*file*]]))

(prn (path/resolve "."))

(prn (term-size))

(println (count (str (fs/readFileSync *file*))))

(prn (sh/ls "."))

(prn (csv-parse "foo,bar"))

(prn (zxfs/existsSync *file*))

(zx/$ #js ["ls"])

Call the script:

$ nbb script.cljs
"/private/tmp/test-script"
#js {:columns 216, :rows 47}
510
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
true
$ ls
node_modules
package-lock.json
package.json
script.cljs

Macros

Nbb has first class support for macros: you can define them right inside your .cljs file, like you are used to from JVM Clojure. Consider the plet macro to make working with promises more palatable:

(defmacro plet
  [bindings & body]
  (let [binding-pairs (reverse (partition 2 bindings))
        body (cons 'do body)]
    (reduce (fn [body [sym expr]]
              (let [expr (list '.resolve 'js/Promise expr)]
                (list '.then expr (list 'clojure.core/fn (vector sym)
                                        body))))
            body
            binding-pairs)))

Using this macro we can look async code more like sync code. Consider this puppeteer example:

(-> (.launch puppeteer)
      (.then (fn [browser]
               (-> (.newPage browser)
                   (.then (fn [page]
                            (-> (.goto page "https://clojure.org")
                                (.then #(.screenshot page #js{:path "screenshot.png"}))
                                (.catch #(js/console.log %))
                                (.then #(.close browser)))))))))

Using plet this becomes:

(plet [browser (.launch puppeteer)
       page (.newPage browser)
       _ (.goto page "https://clojure.org")
       _ (-> (.screenshot page #js{:path "screenshot.png"})
             (.catch #(js/console.log %)))]
      (.close browser))

See the puppeteer example for the full code.

Since v0.0.36, nbb includes promesa which is a library to deal with promises. The above plet macro is similar to promesa.core/let.

Startup time

$ time nbb -e '(+ 1 2 3)'
6
nbb -e '(+ 1 2 3)'   0.17s  user 0.02s system 109% cpu 0.168 total

The baseline startup time for a script is about 170ms seconds on my laptop. When invoked via npx this adds another 300ms or so, so for faster startup, either use a globally installed nbb or use $(npm bin)/nbb script.cljs to bypass npx.

Dependencies

NPM dependencies

Nbb does not depend on any NPM dependencies. All NPM libraries loaded by a script are resolved relative to that script. When using the Reagent module, React is resolved in the same way as any other NPM library.

Classpath

To load .cljs files from local paths or dependencies, you can use the --classpath argument. The current dir is added to the classpath automatically. So if there is a file foo/bar.cljs relative to your current dir, then you can load it via (:require [foo.bar :as fb]). Note that nbb uses the same naming conventions for namespaces and directories as other Clojure tools: foo-bar in the namespace name becomes foo_bar in the directory name.

To load dependencies from the Clojure ecosystem, you can use the Clojure CLI or babashka to download them and produce a classpath:

$ classpath="$(clojure -A:nbb -Spath -Sdeps '{:aliases {:nbb {:replace-deps {com.github.seancorfield/honeysql {:git/tag "v2.0.0-rc5" :git/sha "01c3a55"}}}}}')"

and then feed it to the --classpath argument:

$ nbb --classpath "$classpath" -e "(require '[honey.sql :as sql]) (sql/format {:select :foo :from :bar :where [:= :baz 2]})"
["SELECT foo FROM bar WHERE baz = ?" 2]

Currently nbb only reads from directories, not jar files, so you are encouraged to use git libs. Support for .jar files will be added later.

Current file

The name of the file that is currently being executed is available via nbb.core/*file* or on the metadata of vars:

(ns foo
  (:require [nbb.core :refer [*file*]]))

(prn *file*) ;; "/private/tmp/foo.cljs"

(defn f [])
(prn (:file (meta #'f))) ;; "/private/tmp/foo.cljs"

Reagent

Nbb includes reagent.core which will be lazily loaded when required. You can use this together with ink to create a TUI application:

$ npm install ink

ink-demo.cljs:

(ns ink-demo
  (:require ["ink" :refer [render Text]]
            [reagent.core :as r]))

(defonce state (r/atom 0))

(doseq [n (range 1 11)]
  (js/setTimeout #(swap! state inc) (* n 500)))

(defn hello []
  [:> Text {:color "green"} "Hello, world! " @state])

(render (r/as-element [hello]))

Promesa

Working with callbacks and promises can become tedious. Since nbb v0.0.36 the promesa.core namespace is included with the let and do! macros. An example:

(ns prom
  (:require [promesa.core :as p]))

(defn sleep [ms]
  (js/Promise.
   (fn [resolve _]
     (js/setTimeout resolve ms))))

(defn do-stuff
  []
  (p/do!
   (println "Doing stuff which takes a while")
   (sleep 1000)
   1))

(p/let [a (do-stuff)
        b (inc a)
        c (do-stuff)
        d (+ b c)]
  (prn d))

$ nbb prom.cljs
Doing stuff which takes a while
Doing stuff which takes a while
3

Also see API docs.

Js-interop

Since nbb v0.0.75 applied-science/js-interop is available:

(ns example
  (:require [applied-science.js-interop :as j]))

(def o (j/lit {:a 1 :b 2 :c {:d 1}}))

(prn (j/select-keys o [:a :b])) ;; #js {:a 1, :b 2}
(prn (j/get-in o [:c :d])) ;; 1

Most of this library is supported in nbb, except the following:

• destructuring using :syms
• property access using .-x notation. In nbb, you must use keywords.

See the example of what is currently supported.

Examples

See the examples directory for small examples.

Also check out these projects built with nbb:

• c64core: retrocompute aesthetics twitter bot
• gallery.cljs: script to download walpapers from windowsonearth.org.
• nbb-action-example: example of a Github action built with nbb.

API

See API documentation.

Migrating to shadow-cljs

See this gist on how to convert an nbb script or project to shadow-cljs.

Build

Prequisites:

• babashka >= 0.4.0
• Clojure CLI >= 1.10.3.933
• Node.js 16.5.0 (lower version may work, but this is the one I used to build)

To build:

• Clone and cd into this repo
• bb release

Run bb tasks for more project-related tasks.

Download Details:
Author: borkdude
Download Link: Download The Source Code
Official Website: https://github.com/borkdude/nbb 
License: EPL-1.0

#node #javascript

How to Select and Hire the Best React JS and React Native Developers?

Since March 2020 reached 556 million monthly downloads have increased, It shows that React JS has been steadily growing. React.js also provides a desirable amount of pliancy and efficiency for developing innovative solutions with interactive user interfaces. It’s no surprise that an increasing number of businesses are adopting this technology. How do you select and recruit React.js developers who will propel your project forward? How much does a React developer make? We’ll bring you here all the details you need.

What is React.js?

Facebook built and maintains React.js, an open-source JavaScript library for designing development tools. React.js is used to create single-page applications (SPAs) that can be used in conjunction with React Native to develop native cross-platform apps.

React vs React Native

• React Native is a platform that uses a collection of mobile-specific components provided by the React kit, while React.js is a JavaScript-based library.
• React.js and React Native have similar syntax and workflows, but their implementation is quite different.
• React Native is designed to create native mobile apps that are distinct from those created in Objective-C or Java. React, on the other hand, can be used to develop web apps, hybrid and mobile & desktop applications.
• React Native, in essence, takes the same conceptual UI cornerstones as standard iOS and Android apps and assembles them using React.js syntax to create a rich mobile experience.

What is the Average React Developer Salary?

In the United States, the average React developer salary is $94,205 a year, or $30-$48 per hour, This is one of the highest among JavaScript developers. The starting salary for junior React.js developers is $60,510 per year, rising to $112,480 for senior roles.

* React.js Developer Salary by Country

• United States- $120,000
• Canada - $110,000
• United Kingdom - $71,820
• The Netherlands $49,095
• Spain - $35,423.00
• France - $44,284
• Ukraine - $28,990
• India - $9,843
• Sweden - $55,173
• Singapore - $43,801

In context of software developer wage rates, the United States continues to lead. In high-tech cities like San Francisco and New York, average React developer salaries will hit $98K and $114per year, overall.

However, the need for React.js and React Native developer is outpacing local labour markets. As a result, many businesses have difficulty locating and recruiting them locally.

It’s no surprise that for US and European companies looking for professional and budget engineers, offshore regions like India are becoming especially interesting. This area has a large number of app development companies, a good rate with quality, and a good pool of React.js front-end developers.

As per Linkedin, the country’s IT industry employs over a million React specialists. Furthermore, for the same or less money than hiring a React.js programmer locally, you may recruit someone with much expertise and a broader technical stack.

How to Hire React.js Developers?

• Conduct thorough candidate research, including portfolios and areas of expertise.
• Before you sit down with your interviewing panel, do some homework.
• Examine the final outcome and hire the ideal candidate.

Why is React.js Popular?

React is a very strong framework. React.js makes use of a powerful synchronization method known as Virtual DOM, which compares the current page architecture to the expected page architecture and updates the appropriate components as long as the user input.

React is scalable. it utilises a single language, For server-client side, and mobile platform.

React is steady.React.js is completely adaptable, which means it seldom, if ever, updates the user interface. This enables legacy projects to be updated to the most new edition of React.js without having to change the codebase or make a few small changes.

React is adaptable. It can be conveniently paired with various state administrators (e.g., Redux, Flux, Alt or Reflux) and can be used to implement a number of architectural patterns.

Is there a market for React.js programmers?
The need for React.js developers is rising at an unparalleled rate. React.js is currently used by over one million websites around the world. React is used by Fortune 400+ businesses and popular companies such as Facebook, Twitter, Glassdoor and Cloudflare.

Final thoughts:

As you’ve seen, locating and Hire React js Developer and Hire React Native developer is a difficult challenge. You will have less challenges selecting the correct fit for your projects if you identify growing offshore locations (e.g. India) and take into consideration the details above.

If you want to make this process easier, You can visit our website for more, or else to write a email, we’ll help you to finding top rated React.js and React Native developers easier and with strives to create this operation

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What are hooks in React JS? - INFO AT ONE

In this article, you will learn what are hooks in React JS? and when to use react hooks? React JS is developed by Facebook in the year 2013. There are many students and the new developers who have confusion between react and hooks in react. Well, it is not different, react is a programming language and hooks is a function which is used in react programming language.
Read More:- https://infoatone.com/what-are-hooks-in-react-js/

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