DSC Charusat brings out a "Learning React" Series workshop for you all. So the first workshop of the series is on 19th Sept,20 (Saturday) and it will cover Basics of HTML, CSS and JS with ES6
Sharing code in between react components by using render props. HOC and react prop are some of the best ways to share code in react class components.
#hoc #react #renderprop
Presentation for meetup Submit PHP by Anatoliy Sieryi (Full-Stack developer at Binary Studio)
Video: https://www.youtube.com/edit?video_id=tzQRcMcO1-I&video_referrer=watch
AngularJS is a popular JavaScript framework. It is intended to make the implementation of RIA (Rich Internet Applications) easier and convenient. AngularJS is created and maintained by Google. It is relatively, a new JavaScript framework, which is designed to make the front-end development as simple as possible. AngularJS is a useful tool for standardizing the web application structure and it provides a future template to ensure that the client-side applications are developed much effectively.
This document by RapidValue is written by Gourav Ajmani, Technical Lead, who has been working on AngularJS for a while, and has read many tutorials and blogs on it. According to Gourav, he could never find any article which gives a clear, concise and step-by-step guide to create the project structure and execute the project. So, he has written this document which will help you to create the Project structure and then execute it in a simple manner.
DSC Charusat brings out a "Learning React" Series workshop for you all. So the first workshop of the series is on 19th Sept,20 (Saturday) and it will cover Basics of HTML, CSS and JS with ES6
Sharing code in between react components by using render props. HOC and react prop are some of the best ways to share code in react class components.
#hoc #react #renderprop
Presentation for meetup Submit PHP by Anatoliy Sieryi (Full-Stack developer at Binary Studio)
Video: https://www.youtube.com/edit?video_id=tzQRcMcO1-I&video_referrer=watch
AngularJS is a popular JavaScript framework. It is intended to make the implementation of RIA (Rich Internet Applications) easier and convenient. AngularJS is created and maintained by Google. It is relatively, a new JavaScript framework, which is designed to make the front-end development as simple as possible. AngularJS is a useful tool for standardizing the web application structure and it provides a future template to ensure that the client-side applications are developed much effectively.
This document by RapidValue is written by Gourav Ajmani, Technical Lead, who has been working on AngularJS for a while, and has read many tutorials and blogs on it. According to Gourav, he could never find any article which gives a clear, concise and step-by-step guide to create the project structure and execute the project. So, he has written this document which will help you to create the Project structure and then execute it in a simple manner.
This is the first of 3 parts of GWT Training. It is introduces Ajax and GWT and how to install GWT for Eclipse.
It is for Java Programmers that want to start Ajax development using GWT.
Workshop on how to build Vaadin Add-ons. We introduce two styles of building Vaadin add-on components for Vaadin: integrating an existing GWT widget (DatePicker), and integrating an existing JavaScript library (three.js).
As applications grow in complexity, web developers and front-end developers all suffer the hassle of building and maintaining complex web applications; managing and maintaining consistency of application state. This presentation goes through what's special about React and Redux.
This was part of JOSA TechTalks project within Jordan Open Source Association, presented by Ali Sa'o and Omar Abdelhafith.
React Js Basic Details and Descriptions
Frontend Javascript Library, to make decent SPA
The fastest way to build a segregated component based front end for software development.
Angular 7 Firebase5 CRUD Operations with Reactive FormsDigamber Singh
Learn to create a student record management system app using Angular 7, Firebase5 Database, Reactive Forms, Form Validation, NGX-Pagination and NGX-Toastr.
28.03.15. Одесса. Impact Hub Odessa. Конференция JSLab.
Алексей Волков. "React на практике"
Доклад освещает практические аспекты использования React.js в различном окружении. React и модели Backbone. React и таблицы стилей, а также React в мобильном вебе. Будет полезно как и тем, кто только интересуется этой библиотекой, а также опытным разработчикам.
Подробнее:
http://geekslab.co/
https://www.facebook.com/GeeksLab.co
https://www.youtube.com/user/GeeksLabVideo
Hackathon - Building vaadin add on componentsJoonas Lehtinen
My presentation at Vaadin Hackathon 19-21.4.2013. The presentation outlines all the step of creating a new Vaadin add-on component from design to deployment and publishing.
AngularJS is a JavaScript MVC framework developed by Google that lets you build well structured, easily testable, declarative and maintainable front-end applications which provide solutions to standard infrastructure concerns.
Universal JS Web Applications with React - Luciano Mammino - Codemotion Rome ...Luciano Mammino
Since we started to see JS on the server side, the dream of developers has been to reduce the gap and the cost of switch between frontend/backend technologies. Today with Node.js, React and a whole ecosystem of tools, this dream is becoming real! In this talk, I am going to discuss Universal (a.k.a. Isomorphic) JavaScript and present some practical example regarding the significant patterns related to routing, data retrieval and rendering. I will use Node, React, Webpack, Babel and React Router and give you a series of example to get you started easily with this new technology trend.
(interactive slides at http://slides.com/lucianomammino/universal-js-web-applications-with-react-codemotion-rome-2017 )
This is the first of 3 parts of GWT Training. It is introduces Ajax and GWT and how to install GWT for Eclipse.
It is for Java Programmers that want to start Ajax development using GWT.
Workshop on how to build Vaadin Add-ons. We introduce two styles of building Vaadin add-on components for Vaadin: integrating an existing GWT widget (DatePicker), and integrating an existing JavaScript library (three.js).
As applications grow in complexity, web developers and front-end developers all suffer the hassle of building and maintaining complex web applications; managing and maintaining consistency of application state. This presentation goes through what's special about React and Redux.
This was part of JOSA TechTalks project within Jordan Open Source Association, presented by Ali Sa'o and Omar Abdelhafith.
React Js Basic Details and Descriptions
Frontend Javascript Library, to make decent SPA
The fastest way to build a segregated component based front end for software development.
Angular 7 Firebase5 CRUD Operations with Reactive FormsDigamber Singh
Learn to create a student record management system app using Angular 7, Firebase5 Database, Reactive Forms, Form Validation, NGX-Pagination and NGX-Toastr.
28.03.15. Одесса. Impact Hub Odessa. Конференция JSLab.
Алексей Волков. "React на практике"
Доклад освещает практические аспекты использования React.js в различном окружении. React и модели Backbone. React и таблицы стилей, а также React в мобильном вебе. Будет полезно как и тем, кто только интересуется этой библиотекой, а также опытным разработчикам.
Подробнее:
http://geekslab.co/
https://www.facebook.com/GeeksLab.co
https://www.youtube.com/user/GeeksLabVideo
Hackathon - Building vaadin add on componentsJoonas Lehtinen
My presentation at Vaadin Hackathon 19-21.4.2013. The presentation outlines all the step of creating a new Vaadin add-on component from design to deployment and publishing.
AngularJS is a JavaScript MVC framework developed by Google that lets you build well structured, easily testable, declarative and maintainable front-end applications which provide solutions to standard infrastructure concerns.
Universal JS Web Applications with React - Luciano Mammino - Codemotion Rome ...Luciano Mammino
Since we started to see JS on the server side, the dream of developers has been to reduce the gap and the cost of switch between frontend/backend technologies. Today with Node.js, React and a whole ecosystem of tools, this dream is becoming real! In this talk, I am going to discuss Universal (a.k.a. Isomorphic) JavaScript and present some practical example regarding the significant patterns related to routing, data retrieval and rendering. I will use Node, React, Webpack, Babel and React Router and give you a series of example to get you started easily with this new technology trend.
(interactive slides at http://slides.com/lucianomammino/universal-js-web-applications-with-react-codemotion-rome-2017 )
In this presentation, Prashant Sharma of Valuebound has talked about ReactJS - a JavaScript library for building user interfaces. Check out the agendas to know what is there for you.
----------------------------------------------------------
Get Socialistic
Our website: http://valuebound.com/
LinkedIn: http://bit.ly/2eKgdux
Facebook: https://www.facebook.com/valuebound/
Twitter: http://bit.ly/2gFPTi8
At Lia Infraservice we create Dynamic Websites. Become a front-end React JS developer and be a part of our tech-savvy Web App Development Company in Chennai.
Ways to Set Focus on an Input Field After Rendering in React.pptxBOSC Tech Labs
Here is the complete article on how you can set a focus on the input field after rendering in React. Learn autofocus using React hooks & class components in this article.
Sulok Jha and Ramani Iyengar, engineers at Atlogys Technical Consulting deliver a very informative talk on reactJS - what it is, how to use it, when to use it etc.
This is a must watch for anyone wanting to get started with .reactJS technology.
Паразитируем на React-экосистеме (Angular 4+) / Алексей Охрименко (IPONWEB)Ontico
РИТ++ 2017, Frontend Сonf
Зал Мумбаи, 5 июня, 13:00
Тезисы:
http://frontendconf.ru/2017/abstracts/2470.html
Паразитизм — форма взаимоотношений между организмами различных видов, из которых один (паразит — aka Angular 4+) использует другого (хозяина — aka React) в качестве среды обитания и источника питания, нанося ему вред, но при этом не убивая.
Паразитоид — организм, который проводит значительную часть своей жизни (в личиночной стадии), проживая на или внутри своего единственного хозяина, которого он постепенно убивает в процессе.
...
2.Cellular Networks_The final stage of connectivity is achieved by segmenting...JeyaPerumal1
A cellular network, frequently referred to as a mobile network, is a type of communication system that enables wireless communication between mobile devices. The final stage of connectivity is achieved by segmenting the comprehensive service area into several compact zones, each called a cell.
Instagram has become one of the most popular social media platforms, allowing people to share photos, videos, and stories with their followers. Sometimes, though, you might want to view someone's story without them knowing.
Bridging the Digital Gap Brad Spiegel Macon, GA Initiative.pptxBrad Spiegel Macon GA
Brad Spiegel Macon GA’s journey exemplifies the profound impact that one individual can have on their community. Through his unwavering dedication to digital inclusion, he’s not only bridging the gap in Macon but also setting an example for others to follow.
APNIC Foundation, presented by Ellisha Heppner at the PNG DNS Forum 2024APNIC
Ellisha Heppner, Grant Management Lead, presented an update on APNIC Foundation to the PNG DNS Forum held from 6 to 10 May, 2024 in Port Moresby, Papua New Guinea.
Gen Z and the marketplaces - let's translate their needsLaura Szabó
The product workshop focused on exploring the requirements of Generation Z in relation to marketplace dynamics. We delved into their specific needs, examined the specifics in their shopping preferences, and analyzed their preferred methods for accessing information and making purchases within a marketplace. Through the study of real-life cases , we tried to gain valuable insights into enhancing the marketplace experience for Generation Z.
The workshop was held on the DMA Conference in Vienna June 2024.
Italy Agriculture Equipment Market Outlook to 2027harveenkaur52
Agriculture and Animal Care
Ken Research has an expertise in Agriculture and Animal Care sector and offer vast collection of information related to all major aspects such as Agriculture equipment, Crop Protection, Seed, Agriculture Chemical, Fertilizers, Protected Cultivators, Palm Oil, Hybrid Seed, Animal Feed additives and many more.
Our continuous study and findings in agriculture sector provide better insights to companies dealing with related product and services, government and agriculture associations, researchers and students to well understand the present and expected scenario.
Our Animal care category provides solutions on Animal Healthcare and related products and services, including, animal feed additives, vaccination
Understanding User Behavior with Google Analytics.pdfSEO Article Boost
Unlocking the full potential of Google Analytics is crucial for understanding and optimizing your website’s performance. This guide dives deep into the essential aspects of Google Analytics, from analyzing traffic sources to understanding user demographics and tracking user engagement.
Traffic Sources Analysis:
Discover where your website traffic originates. By examining the Acquisition section, you can identify whether visitors come from organic search, paid campaigns, direct visits, social media, or referral links. This knowledge helps in refining marketing strategies and optimizing resource allocation.
User Demographics Insights:
Gain a comprehensive view of your audience by exploring demographic data in the Audience section. Understand age, gender, and interests to tailor your marketing strategies effectively. Leverage this information to create personalized content and improve user engagement and conversion rates.
Tracking User Engagement:
Learn how to measure user interaction with your site through key metrics like bounce rate, average session duration, and pages per session. Enhance user experience by analyzing engagement metrics and implementing strategies to keep visitors engaged.
Conversion Rate Optimization:
Understand the importance of conversion rates and how to track them using Google Analytics. Set up Goals, analyze conversion funnels, segment your audience, and employ A/B testing to optimize your website for higher conversions. Utilize ecommerce tracking and multi-channel funnels for a detailed view of your sales performance and marketing channel contributions.
Custom Reports and Dashboards:
Create custom reports and dashboards to visualize and interpret data relevant to your business goals. Use advanced filters, segments, and visualization options to gain deeper insights. Incorporate custom dimensions and metrics for tailored data analysis. Integrate external data sources to enrich your analytics and make well-informed decisions.
This guide is designed to help you harness the power of Google Analytics for making data-driven decisions that enhance website performance and achieve your digital marketing objectives. Whether you are looking to improve SEO, refine your social media strategy, or boost conversion rates, understanding and utilizing Google Analytics is essential for your success.
Understanding User Behavior with Google Analytics.pdf
Introduction to React for Frontend Developers
1. Sergio Nakamura | nakamurasei.com hi@nakamurasei.com
An Introduction
To React For
Frontend Developers
2. An Introduction To React For Frontend Developers hi@nakamurasei.com
Disclaimer
Many of the techniques displayed aren’t exclusive to React. In fact, React is
built in JavaScript and as such all React features can be implemented in
JavaScript (and have existed for years, albeit with less flashy names).
However React offers a “framework”, a structure you can use to build your
applications. While not many people will implement a pub-sub method or a
helper method to simplify element creation, many people will use a
framework. You can use its features without knowing its inner workings,
without reinventing the wheel, and using the same conventions.
3. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
JavaScript has been used for over two decades to add interactivity to
webpages: adding, removing or modifying elements, responding to user
input and sending and receiving data from external sources.
React (just like Angular, Vue and many more) are frameworks built on
JavaScript that allow easier development of user interfaces.
1.
Declarative
Style
2.
Automatic
Updates
3.
Virtual
DOM
4.
Modular
Structure
4. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
Declarative Style
If you’ve previously used JavaScript you may have found yourself telling the
browser each step to make: select X element, set the content to Y, do Z
when clicked... Having to tell each step can be classified as an
“Imperative” style: forgetting a step may lead to errors, because the browser
just follows instructions, it doesn’t know what you’re actually looking for.
In React, you are following most of the time a “Declarative” style, you tell
what you want and provide the data. React does the work behind the
scenes to translate that information to the instructions your browser
understands.
1
5. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
Declarative Style
Let’s render a <button> and console.log when clicked, in Vanilla JS and React.
Vanilla JS React JS
1
const btn =
document.createElement(“button”);
//Create <button>
body.appendChild(btn); //Append to body
btn.innerText = “Click me”; //Change text
btn.addEventListener(“click”, () => {
console.log(“Clicked”);
}); //Log “Clicked” when clicked
import React from “react”;
export default function App() {
return (
<button onClick={() =>
console.log(“Clicked”)}>
Click me
</button>
);
} //I want a <button> with “Click me” as
text that logs “Clicked” when clicked
6. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
Automatic Updates
As your application grows adding an element and setting a value isn’t
enough: you may need to update its content as you receive new
information.
Without a framework as React, you may have to tell the browser to update the
elements every time we receive new information. While this doesn’t seem a
big deal at first it can get ugly fast.
Using React, all the elements depending on a piece of data get updated
automatically when the data changes.
2
7. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
Automatic Updates
Let’s see a simple button that +1 to a counter. The counter variable is seen in
two places at the time.
2
Vanilla JS React JS
let counter = 0; //Counter
const p = document.createElement(“p”); //Create a <p>
p.innerText = counter; //Set <p>’s text
body.appendChild(p); //Append <p> to the body
const btn = document.createElement(“button”);
//Create a <button>
btn.innerText = `+1 and make it ${counter + 1}`;
//Set <button>’s text
body.appendChild(btn);
//Append <button> to the body
btn.addEventListener(“click”, () => {
counter = counter ++; //Update the counter
p.innerText = counter; //Update <p>
btn.innerText = `+1 and make it ${counter + 1}`;
// Update <btn>
})
import React, {useState} from “react”;
export default function App() {
const [counter, setCounter] = useState(0);
return (<div>
<p>{counter}</p>
<button onClick={() =>
setCounter(counter++)}>
`+1 and make it ${counter + 1}`
</button>
</div>)
}
//All elements depending on counter will update when
counter changes value
8. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
Virtual DOM
In JavaScript one of the most performance degrading actions is updating
the DOM, that is the elements that compose your webpage. As such, wouldn’t
be great if we updated the DOM as less as possible? Enter the Virtual DOM.
With React we have two versions of the DOM: the one that’s being displayed
in the browser and an internal DOM that reflects the processed output by
React. By comparing both DOMs we can update only the elements that we
need. Without some technique like Virtual DOM we may need to update all
the elements even if we modified only one, incurring a performance hit.
3
9. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
Modular Structure
In React, each part of the UI can be divided in smaller components. This
makes coding more manageable and easier to work in a team, it allows the
production of self-contained components that can be reused easily and since
it’s JavaScript it allows data passing between components: no more storing
data in the DOM and in humongous global states.
4
10. An Introduction To React For Frontend Developers hi@nakamurasei.com
Why React?
Modular Structure
Let’s see how components can make our code more manageable.
4
Vanilla JS React JS
let fruits = [“mango”, “apple”, “banana”, “orange”];
const div = document.createElement(“div”);
//Create <div>
body.appendChild(div); //Append to body
function addFruits() {
fruits.forEach(fruit => {
const p = document.createElement(“p”);
p.innerText = fruit;
div.appendChild(p);})
}
addFruits();
import React, {useState, useEffect} from “react”;
import Fruits from “./Fruits.js”;
export default function App() {
const [fruits, setFruits] = useState([“mango”,
“apple”, “banana”, “orange”]);
return (<Fruits fruits={fruits}/>);
}
import React, {useState, useEffect} from “react”;
export default function Fruits(props) {
return (<div>{props.fruits.map(fruit=><p
key={fruit}>{fruit}</p>)}</div>);
}
//”fruits” was received from App() via props
App.js
Fruits.js
11. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
You can build a React application with either classes or functions. While
classes are useful when building complex components, in most cases using
functions will be more readable and concise.
You can build functional components in these ways. Note that we are
exporting the function, so we can use it in another place.
import React from “react”;
export default function App() {
return(<p>Hello World</p>);
}
import React from “react”;
const App = () => {
return(<p>Hello World</p>);
}
export default App;
12. An Introduction To React For Frontend Developers hi@nakamurasei.com
What you are seeing in orange isn’t HTML, is something called JSX, an
extension of JavaScript used in React. When you are using JSX you are
actually calling a function named “createElement” which outputs the HTML
you are expecting.
React Basics
JSX
import React from “react”;
export default function App() {
return(<p>Hello World</p>);
}
13. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
JSX
JSX elements must be closed at all times. While most HTML elements follow
the <></> structure, some elements don’t have an end tag (like <input> or
<img>). In those cases you must add a / right before >, effectively closing it.
<input type=”submit”> <input type=”submit”/>
HTML React’s JSX
14. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
JSX
As we are seeing, JSX isn’t an exact copy of HTML. If you want to style your
components using CSS, the “class” property isn’t allowed. Instead, use
“className”.
<p class=”hello”>Hello</p> <p className=”hello”>Hello</p>
HTML React’s JSX
15. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
JSX
One of the advantages of JSX is that we can use JavaScript code instead of
strings. To do so we wrap our code in {}. This allows us to use variables,
render CSS class names conditionally, call functions and more.
<p className=”hello”>{message}</p>
//<p>’s content is the variable “message”.
React’s JSX
16. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
JSX - Using JS Code inside {}
The code inside {} must always return something (even null).
We can’t add more than one line (as in separate instructions divided by ;),
however functions can have multiples lines inside it.
<p className=”hello”>{
function renderStuff () {
return “Hello”
};
renderStuff()}
</p>
<p className=”hello”>{
“Hello”
}</p>
Invalid: Separate instructions OK
17. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
JSX - Using JS Code inside {}
We can’t use if as it doesn’t always return something. We can use a ternary
expression instead, where the else clause returns null.
<p className=”hello”>{
if(name === “Kentaro”){
return “You are
Kentaro”}
}</p>
<p className=”hello”>{
name === “Kentaro” ? “You are
Kentaro” : null
}</p>
Invalid: if OK
18. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
JSX - Using JS Code inside {}
To replace an if else clause use the ternary expression in the same way.
<p className=”hello”>{
if(name === “Kentaro”){
return “You are
Kentaro”} else {
return “You are not Kentaro”
}
}</p>
<p className=”hello”>{
name === “Kentaro” ? “You are
Kentaro” : “You are not Kentaro”
}</p>
Invalid: if OK
19. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
JSX - Using JS Code inside {}
We can’t add loops (such as for or forEach). However we can use array’s map,
since it will always return an array.
<div>{
names.forEach(name => <p
key={name}>{name}</p>)}
</div>
<div>{
names.map(name => <p
key={name}>{name}</p>)
}</div>
Invalid: forEach
<div>{
for(i = 0, n=names.length; i<n; i++){
return <p key={names[i]}>names[i]</p>}
}</div>
Invalid: for
OK
20. An Introduction To React For Frontend Developers hi@nakamurasei.com
import React from “react”;
import MyFunction from “./MyFunction.js”;
const App = () => {
return <MyFunction name=”Kentaro”/>;
}
export default App;
App.js
import React from “react”;
const MyFunction = (props) => {
return <p>{props.name}</p>;
}
export default MyFunction;
MyFunction.js
React Basics
Modularity
By splitting your application in several files code reuse and teamwork become
easier. To import a component use “import” at the top of your file.
21. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
Using state inside components
To store information inside our components we can use “useState”, a React
Hook (function that enables access to the state and lifecycle features of
React.)
import React, {useState} from “react”; import React, {useState} from “react”;
export default function App() {
const [counter, setCounter] =
useState(0);
return <p>{counter}</p>;
}
1: Import useState at the top 2. Call useState inside the function
22. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
Anatomy of useState
const [counter, setCounter] = useState(0);
1: Pick a name for the
variable that will hold the
state’s value.
2: This is the function that will
set the state’s value.
By convention name it “set” +
the name picked in 1
(camelCase).
3: This is the initial value of
the state. Ideally set it to the
same type as the expected
value. For example, if you are
expecting a number you can
set it to 0.
Functions, variables, even null
and undefined is OK.
23. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
useState example
import React, {useState} from “react”;
export default function App() {
const [counter, setCounter] =
useState(0);
return (<div>
<p>{counter}</p>
<button onClick={() =>
setCounter(counter + 1)}>+1</button>
</div>
)
}
1: <p/> will hold the counter value. At
initialization its value will be 0, as defined in
useState.
2: When <button/> is clicked, the counter’s
value will be incremented by 1. Automatically,
every place that holds “counter” will update its
value.
24. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
useEffect
Another React Hook is “useEffect”. Whatever instructions are inside of
useEffect will get executed whenever there’s an update to its dependences.
This lets us fetch data at component mount, execute functions when new
information is received and more.
import React, {useEffect} from “react”; import React, {useEffect} from “react”;
export default function App() {
useEffect(() => {
//Place code here
}, []);
return <p>Hello world</p>;
}
1: Import useEffect at the top 2. Call useEffect inside the function
25. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
useEffect’s Behaviour
The behaviour of useEffect changes depending on the dependencies defined
in the [] at the end.
useEffect(() => {
//Place code here
}, []);
Component mount
If nothing is defined inside [], the code inside
useEffect will execute only once at
component mount. This replaces React’s
lifecycle method componentDidMount.
useEffect(() => {
//Place code here
}, [varName]);
Update at dependency change
The code will execute once at component
mount and everytime there’s a change of the
dependencies defined inside []. You can add as
many dependencies you wish.
26. An Introduction To React For Frontend Developers hi@nakamurasei.com
React Basics
useEffect example
import React, {useState, useEffect} from
“react”;
export default function App() {
const [counter, setCounter] =
useState(0);
useEffect(()=>{
console.log(`Counter value is
${counter}`);
}, [counter]);
return (<div>
<p>{counter}</p>
<button onClick={() =>
setCounter(counter + 1)}>+1</button>
</div>
)
}
Because “counter” is defined as a dependency
of useEffect, it will console.log every time
“counter” is incremented.