Karim Aya

Karim Aya

1565748508

Demystifying this in JavaScript and React

Originally published by Nabendu Biswas at medium.com

It is such a big topic, that if you need to master it you need to go through a whole book by Kyle Simpson — **You don’t know JS: this & object prototypes. **You can find the free version of the book here.

We will understand this in JavaScript first then will move to the this.bindfor react.

Understanding “this” in JS

Objects are the basics of JavaScript, even functions are object in JavaScript. Now “this” is a special object in JavaScript and it’s value is decided on how the code is executed.

“this” in simple function

In a normal JS function like below, the “this” refers to global window object.

function foo() {
  console.log(this);
  console.log(this === window);  
}

foo();

Running the above code will give.

global window object

There is a special case with strict mode.

In strict mode “this” to be undefined , as global object refers to undefined instead of window object.
function foo() {
‘use strict’;
console.log(this);
console.log(this === window);
}

foo();

this is undefined

“this” in a object property

In a object which have a property as a function, the value of “this” is the Object itself.

var obj = {};
obj.foo = function() {
console.log(“Inside obj foo”);
console.log(this);
}

obj.foo();

this is Object itself

“this” with constructor function

When a function is called with “new” keyword, it is know as constructor function. And the value of “this” refers to the newly created instance.

function Person(fn, ln) {
this.first_name = fn;
this.last_name = ln;

this.displayName = function() {
console.log(Name: ${this.first_name} ${this.last_name});
console.log(this);
}
}

let person = new Person(“Nabendu”, “Biswas”);
person.displayName();
let person2 = new Person(“Shikha”, “Biswas”);
person2.displayName();


The newly created instance is nothing but an object, because everything in JS is a object.

this refers to newly created Object

“this” with call, apply and bind method

Almost everything in JavaScript is an object,including functions. Every functions have call, apply and bind methods. These methods can be used to set the custom value of “this” to the execution context of the function.

call

Let’s say that we have an object called obj. It only has one property called num, which has a value of 3. Let’s also make a function called addNumbers.

let obj = {num: 3};
let addNumbers = function(a, b, c){
console.log(this);
return this.num + a + b + c;
};

Now, in addNumbers we have this.num. But how do we pass the value obj.num to it. We need to pass it a context, which means the value of “this”. We will do this my call method by passing a first argument as obj, so the “this” is the obj now.

this is obj

apply

It is totally similar to call, but the only difference is that we can pass array as the second argument. We will use the same code for apply also.

let obj = {num: 3};
let addNumbers = function(a, b, c){
console.log(this);
return this.num + a + b + c;
};

But now we have an arr, to be passed as second argument.

arr as second argument

bind

Bind works in a bit different way then call and apply. It works by returning a copy of the function. So, we will use the same code.

let obj = {num: 3};
let addNumbers = function(a, b, c){
console.log(this);
return this.num + a + b + c;
};

We will take the returned function in bindFunc and then execute it in the next line.

bind explained

Understanding “this” in React

Anyone who have worked with React, must have used the bind function inside the constructor for a function which was called through an input event.

class Foo extends React.Component{
constructor( props ){
super( props );
this.state = {
text: ‘’
}

this.handleChange = this.handleChange.bind(this);
}

handleChange(event){
this.setState({
text: event.target.value
})
}

render(){
return (
<input type=“text” value={this.state.text}
onChange={this.handleChange} />
);
}
}

ReactDOM.render(
<Foo />,
document.getElementById(“app”)
);

If we don’t give the line this.handleChange = this.handleChange.bind(this), then handleChange() will throw error that

‘this’ is undefined

This issue occurs because of JavaScript and not React. Let’s recreate this issue in plain JavaScript. Running the code in Firefox scratchpad gives error.

class Foo {
constructor(name){
this.name = name
}
display(){
console.log(this.name);
}
}
var foo = new Foo(‘Nabendu’);
foo.display(); //Outputs Nabendu

var display = foo.display;
display();
/
Exception: TypeError: this is undefined
display@Scratchpad/1:6:5
@Scratchpad/1:13:1
/

The assignment operation below simulates loss of context, similar to passing the handler as a callback in the actual React Component.

This gives undefined because the bodies of classes are by default in strict mode and in strict mode the global object is undefined.

To prevent this error we need to bind “this” value.

class Foo {
constructor(name){
this.name = name;
this.display = this.display.bind(this);
}
display(){
console.log(this.name);
}
}
var foo = new Foo(‘Nabendu’);
foo.display(); //Outputs Nabendu

var display = foo.display;
display(); //Outputs Nabendu

The same thing happens in React. When we bind the “this” of the event handler to the component instance in the constructor, we can pass it as a callback without worrying about it losing its context.

“arrow” function in the callback

We can also avoid the bind statement by using arrow function in callback.

class Foo extends React.Component{
constructor( props ){
super( props );
this.state = {
text: ‘’
}
}

handleChange(event){
this.setState({
text: event.target.value
})
}

render(){
return (
<input type=“text” value={this.state.text}
onChange={(e) => this.handleChange(e)} />
);
}
}

ReactDOM.render(
<Foo />,
document.getElementById(“app”)
);

The reason is that in the case of arrow functions, “this” is bound lexically. This means that it uses the context of the enclosing function — or global — scope as its “this” value.

Originally published by Nabendu at medium.com

===========================================

Thanks for reading :heart: If you liked this post, share it with all of your programming buddies! Follow me on Facebook | Twitter

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#javascript #reactjs #web-development

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Buddha Community

Demystifying this in JavaScript and React
Autumn  Blick

Autumn Blick

1598839687

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.

#android app #frontend #ios app #mobile app development #benefits of react native #is react native good for mobile app development #native vs #pros and cons of react native #react mobile development #react native development #react native experience #react native framework #react native ios vs android #react native pros and cons #react native vs android #react native vs native #react native vs native performance #react vs native #why react native #why use react native

Mathew Rini

1615544450

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

#hire-react-js-developer #hire-react-native-developer #react #react-native #react-js #hire-react-js-programmer

Franz  Becker

Franz Becker

1651604400

React Starter Kit: Build Web Apps with React, Relay and GraphQL.

React Starter Kit — "isomorphic" web app boilerplate   

React Starter Kit is an opinionated boilerplate for web development built on top of Node.js, Express, GraphQL and React, containing modern web development tools such as Webpack, Babel and Browsersync. Helping you to stay productive following the best practices. A solid starting point for both professionals and newcomers to the industry.

See getting started guide, demo, docs, roadmap  |  Join #react-starter-kit chat room on Gitter  |  Visit our sponsors:

 

Hiring

Getting Started

Customization

The master branch of React Starter Kit doesn't include a Flux implementation or any other advanced integrations. Nevertheless, we have some integrations available to you in feature branches that you can use either as a reference or merge into your project:

You can see status of most reasonable merge combination as PRs labeled as TRACKING

If you think that any of these features should be on master, or vice versa, some features should removed from the master branch, please let us know. We love your feedback!

Comparison

 

React Starter Kit

React Static Boilerplate

ASP.NET Core Starter Kit

App typeIsomorphic (universal)Single-page applicationSingle-page application
Frontend
LanguageJavaScript (ES2015+, JSX)JavaScript (ES2015+, JSX)JavaScript (ES2015+, JSX)
LibrariesReact, History, Universal RouterReact, History, ReduxReact, History, Redux
RoutesImperative (functional)DeclarativeDeclarative, cross-stack
Backend
LanguageJavaScript (ES2015+, JSX)n/aC#, F#
LibrariesNode.js, Express, Sequelize,
GraphQL
n/aASP.NET Core, EF Core,
ASP.NET Identity
SSRYesn/an/a
Data APIGraphQLn/aWeb API

Backers

♥ React Starter Kit? Help us keep it alive by donating funds to cover project expenses via OpenCollective or Bountysource!

lehneres Tarkan Anlar Morten Olsen Adam David Ernst Zane Hitchcox  

How to Contribute

Anyone and everyone is welcome to contribute to this project. The best way to start is by checking our open issues, submit a new issue or feature request, participate in discussions, upvote or downvote the issues you like or dislike, send pull requests.

Learn More

Related Projects

  • GraphQL Starter Kit — Boilerplate for building data APIs with Node.js, JavaScript (via Babel) and GraphQL
  • Membership Database — SQL schema boilerplate for user accounts, profiles, roles, and auth claims
  • Babel Starter Kit — Boilerplate for authoring JavaScript/React.js libraries

Support

License

Copyright © 2014-present Kriasoft, LLC. This source code is licensed under the MIT license found in the LICENSE.txt file. The documentation to the project is licensed under the CC BY-SA 4.0 license.


Author: kriasoft
Source Code: https://github.com/kriasoft/react-starter-kit
License: MIT License

#graphql #react 

Juned Ghanchi

1621573085

React Native App Developers India, React Native App Development Company

Expand your user base by using react-native apps developed by our expert team for various platforms like Android, Android TV, iOS, macOS, tvOS, the Web, Windows, and UWP.

We help businesses to scale up the process and achieve greater performance by providing the best react native app development services. Our skilled and experienced team’s apps have delivered all the expected results for our clients across the world.

To achieve growth for your business, hire react native app developers in India. You can count on us for all the technical services and support.

#react native app development company india #react native app developers india #hire react native developers india #react native app development company #react native app developers #hire react native developers

The Ugly Side of React Hooks

In this post, I will share my own point of view about React Hooks, and as the title of this post implies, I am not a big fan.

Let’s break down the motivation for ditching classes in favor of hooks, as described in the official React’s docs.

Motivation #1: Classes are confusing

we’ve found that classes can be a large barrier to learning React. You have to understand how "this"_ works in JavaScript, which is very different from how it works in most languages. You have to remember to bind the event handlers. Without unstable syntax proposals, the code is very verbose […] The distinction between function and class components in React and when to use each one leads to disagreements even between experienced React developers._

Ok, I can agree that

thiscould be a bit confusing when you are just starting your way in Javascript, but arrow functions solve the confusion, and calling a_stage 3_feature that is already being supported out of the box by Typescript, an “unstable syntax proposal”, is just pure demagoguery. React team is referring to theclass fieldsyntax, a syntax that is already being vastly used and will probably soon be officially supported

class Foo extends React.Component {
  onPress = () => {
    console.log(this.props.someProp);
  }

  render() {
    return <Button onPress={this.onPress} />
  }
}

As you can see, by using a class field arrow function, you don’t need to bind anything in the constructor, and

this will always point to the correct context.

And if classes are confusing, what can we say about the new hooked functions? A hooked function is not a regular function, because it has state, it has a weird looking

this(aka_useRef_), and it can have multiple instances. But it is definitely not a class, it is something in between, and from now on I will refer to it as aFunclass. So, are those Funclasses going to be easier for human and machines? I am not sure about machines, but I really don’t think that Funclasses are conceptually easier to understand than classes. Classes are a well known and thought out concept, and every developer is familiar with the concept ofthis, even if in javascript it’s a bit different. Funclasses on the other hand, are a new concept, and a pretty weird one. They feel much more magical, and they rely too much on conventions instead of a strict syntax. You have to follow somestrict and weird rules, you need to be careful of where you put your code, and there are many pitfalls. Telling me to avoid putting a hook inside anifstatement, because the internal mechanism of hooks is based on call order, is just insane! I would expect something like this from a half baked POC library, not from a well known library like React. Be also prepared for some awful naming like useRef (a fancy name forthis),useEffect ,useMemo,useImperativeHandle(say whatt??) and more.

The syntax of classes was specifically invented in order to deal with the concept of multiple instances and the concept of an instance scope (the exact purpose of

this ). Funclasses are just a weird way of achieving the same goal, using the wrong puzzle pieces. Many people are confusing Funclasses with functional programming, but Funclasses are actually just classes in disguise. A class is a concept, not a syntax.

Oh, and about the last note:

The distinction between function and class components in React and when to use each one leads to disagreements even between experienced React developers

Until now, the distinction was pretty clear- if you needed a state or lifecycle methods, you used a class, otherwise it doesn’t really matter if you used a function or class. Personally, I liked the idea that when I stumbled upon a function component, I could immediately know that this is a “dumb component” without a state. Sadly, with the introduction of Funclasses, this is not the situation anymore.

#react #react-hooks #javascript #reactjs #react-native #react-hook #rethinking-programming #hackernoon-top-story