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<h2>Introduction</h2>
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React Home
</button>
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React Setup
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React Getting Started
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React ES6
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React Render HTML
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React JSX
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React Components
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React Class
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React Props
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React Events
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React Conditional
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React Lists
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React Forms
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React Router
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React Memo
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React CSS Styling
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What is a Hook?
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React useState Hook
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React useEffect Hook
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React useContext
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React useRef
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React useReducer
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React useCallback
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React useMemo
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<div class="notes" id="div1">
<h2>React Home</h2>
<br />
<h3>What is ReactJS?</h3>
<br />
<p>
ReactJS is a <b>JavaScript</b> library used to build User
Interfaces(UI). It significantly decreases the code with it's
components, states i.e. hooks, etc.
</p>
<br />
<h3>Creating react app</h3>
<br />
<p>
Open your terminal in the directory you would like to create your
application. Run this command to create a React application named
my-react-app:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
npx create-react-app my-react-app
</code>
</pre>
<br />
<br />
<p>
OR, you can directly make your application without specifying a
name, like this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
npx create-react-app .
</code>
</pre>
<br />
<br />
<p>
In this case, all files will be kept in the current directory.
<br />
<b>Note:</b>When choosing folder name, make sure there are no
spaces or capital letters because of npm naming restrictions.
<br />
Once base application is created, if folder specified you just
have to enter the folder. You can use this command to enter:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
cd directory-name
</code>
</pre>
<br />
<br />
<p>Then just start up the application with this command:</p>
<br />
<pre class="highlight">
<code class="language-JS">
npm start
</code>
</pre>
<br />
<br />
<p>and you are good to go!</p>
<br />
<h3>Hello World</h3>
<br />
<pre class="highlight">
<code class="language-JS">
const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(<h1>Hello, world!</h1>);
</code>
</pre>
<br />
<br />
<p>
In this we are just putting <h1> tag in a div with id
'root'. That's it! In div with id 'root' everything will be
rendered. We can also change it from 'root' to something else, as
we are just getting an element and putting HTML in it.
</p>
<br />
<br />
</div>
<div class="notes" id="div2" style="display: none">
<h2>React Setup</h2>
<br />
<h3>Node.js</h3>
<br />
<p>You can download it from: https://nodejs.org/en/</p>
<br />
<h3>Creating our first react app</h3>
<br />
<p>
Open your terminal in the directory you would like to create your
application. Run this command to create a React application named
my-react-app:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
npx create-react-app my-react-app
</code>
</pre>
<br />
<br />
<p>
OR, you can directly make your application without specifying a
name, like this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
npx create-react-app .
</code>
</pre>
<br />
<br />
<p>
In this case, all files will be kept in the current directory.
<br />
<b>Note:</b> When choosing folder name, make sure there are no
spaces or capital letters because of npm naming restrictions.
<br />
Once base application is created, if folder specified you just
have to enter the folder. You can use this command to enter:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
cd directory-name
</code>
</pre>
<br />
<br />
<p>Then just start up the application with this command:</p>
<br />
<pre class="highlight">
<code class="language-JS">
npm start
</code>
</pre>
<br />
<br />
<p>and you are good to go!</p>
<br />
<br />
</div>
<div class="notes" id="div3" style="display: none">
<h2>React Getting Started</h2>
<br />
<h3>Run and Check</h3>
<br />
<p>
Run the React Application with this command:
<br />
A new browser window will pop up, if it does't then go on
http://localhost:3000/. Check if it is showing the same page:
</p>
<br />
<img
src="https://cwh-full-next-space.fra1.digitaloceanspaces.com/tutorial/react-getting-started/react-intro-page.png"
alt="" /><br />
<p>If it's the same page then you are good to go!</p>
<br />
<h3>Hello World</h3>
<br />
<p>
For this first you need to navigate to src/App.js, it will look
like:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
import logo from './logo.svg';
import './App.css';
function App() {
return (
<div className="App"
<header className="App-header">
<img src={logo} className="App-logo" alt="logo" />
<p>
Edit <code>src/App.js</code>
and save to reload.
</p>
<a
className="App-link"
href="https://reactjs.org"
target="_blank"
rel="noopener noreferrer"
>
Learn React
</a>
</header>
</div>
);
}
export default App;
</code>
</pre>
<br />
<br />
<p>
Whatever you put in return will be rendered as HTML on the page,
you can change it like:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
function App() {
return (
<div className="App">
Hello World
</div>
);
}
</code>
</pre>
<br />
<br />
<p>
<b>Note:</b>Remember to wrap whole return value in an HTML element
as you can't return multiple elements but you can return multiple
elements in one element.
<br />
Page would look like this:
</p>
<br />
<img
src="https://cwh-full-next-space.fra1.digitaloceanspaces.com/tutorial/react-getting-started/react-hello-world.png"
alt="" /><br />
<br />
</div>
<div class="notes" id="div4" style="display: none">
<h2>React ES6</h2>
<br />
<h3>What is ES6?</h3>
<br />
<p>
ES6 stands for ECMAScript 6. ECMAScript is a JavaScript standard
intended to ensure a common language across different browsers.
ES6 is the 6th version of ECMAScript.
</p>
<br />
<h3>Why ES6? / Features of ES6 / Upgrades in ES6</h3>
<br />
<p>
React uses ES6 and all of these new features will make your coding
experience in react much much better. You will be able to do
things with much more ease and in very less lines! Features like:
</p>
<br />
<li><b>Arrow Functions:</b></li>
<br />
<pre class="highlight">
<code class="language-JS">
const hello = () => {
return "Hello World!";
}
</code>
</pre>
<br />
<br />
<p>Or</p>
<br />
<pre class="highlight">
<code class="language-JS">
const hello = () => "Hello World!";
</code>
</pre>
<br />
<br />
<li>
<b>.map():</b>
<color>.map</color> can be used for alot of things, one of it's
use case is, we can make any number of cards through loop and just
put it in jsx, like this:
</li>
<br />
<pre class="highlight">
<code class="language-JS">
const data = ['title1', 'title2', 'title3'];
let cards = data.map((item) => <card>{item}</card>)
</code>
</pre>
<br />
<br />
<li><b>Destructuring:</b></li>
<br />
<p>Old way:</p>
<br />
<pre class="highlight">
<code class="language-JS">
const languages = ['JS', 'Python', 'Java'];
const js = languages[0]
const python = languages[1]
const java = languages[2]
</code>
</pre>
<br />
<br />
<p>New way:</p>
<br />
<pre class="highlight">
<code class="language-JS">
const languages = ['JS', 'Python', 'Java'];
const [ js, python, java ] = languages
</code>
</pre>
<br />
<br />
<li>
<b>Ternary Operator:</b> With this, you can write if/else
conditions in one line. It's syntax is fairly simple like this:
</li>
<br />
<pre class="highlight">
<code class="language-JS">
condition ? <expression if true> : <expression if false>
</code>
</pre>
<br />
<br />
<h4>Example:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
let loading = false;
const data = loading ? <div>Loading...</div> : <div>Data</div>
</code>
</pre>
<br />
<br />
<li><b>Spread Operator:</b></li>
<br />
<pre class="highlight">
<code class="language-JS">
const languages = ['JS', 'Python', 'Java'];
const morelanguages = ['C', 'C++', 'C#']
const allLanguages = [...languages, ...morelanguages]
</code>
</pre>
<br />
<br />
<h4>Output:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
["JS","Python","Java","C","C++","C#"]
</code>
</pre>
<br />
<br />
<p>and many more like, classes, modules.</p>
<br />
<br />
</div>
<div class="notes" id="div5" style="display: none">
<h2>React Render HTML</h2>
<br />
<p>
React renders HTML to the web page by using a function called
<color>ReactDOM.render().</color>
</p>
<br />
<h3>ReactDOM.render()</h3>
<br />
<p>
This function takes two arguments, HTML content which you want to
show on page and HTML element where you want to put the HTML
content(first argument). But where will it find that element? It
will find it inside "index.html" located in "public" folder. There
you will notice a <color>div</color> with id "root". That is where
all this will be rendered!
</p>
<br />
<pre class="highlight">
<code class="language-JS">
ReactDOM.render(<p>Hello</p>, document.getElementById('root'));
</code>
</pre>
<br />
<br />
<img src="https://cwh-full-next-space.fra1.digitaloceanspaces.com/tutorial/react-render-html/id-root.png"
alt="" /><br />
<br />
</div>
<div class="notes" id="div6" style="display: none">
<h2>React JSX</h2>
<br />
<h3>What is JSX?</h3>
<br />
<p>
JSX stands for JavaScript XML. It is similar in appearance to
HTML, hence provides a way to easily write HTML in react.
</p>
<br />
<h3>Coding in JSX</h3>
<br />
<p>
Earlier we had to make an HTML element or append it into existing
ones with methods like
<color>createElement() / appendChild().</color>
</p>
<br />
<pre class="highlight">
<code class="language-JS">
const elem = React.createElement('h1', {}, 'Hello World!');
</code>
</pre>
<br />
<br />
<p>Now we can just do it directly, like this:</p>
<br />
<pre class="highlight">
<code class="language-JS">
const elem = <h1>Hello World!</h1>
</code>
</pre>
<br />
<br />
<h3>Expressions in JSX</h3>
<br />
<p>
You can write the expression in {}
<br />
You can write simple mathematical operations to variable to states
to complicated operations with ternary operators and it will
return the result, like:
</p>
<br />
<h4>Mathematical Operations:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
const elem = <h1>React was released in {2010+3}</h1>
</code>
</pre>
<br />
<br />
<h4>Variables/states:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
const name = "CWH"
const elem = <h1>My name is {name}</h1>
</code>
</pre>
<br />
<br />
<h4>Ternary Operators:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
const elem = <h1>Hello {name ? name : 'World'}</h1>
</code>
</pre>
<br />
<br />
</div>
<div class="notes" id="div7" style="display: none">
<h2>React Components</h2>
<br />
<p>There are two types of components:</p>
<br />
<li>Class Based Components</li>
<li>Function Based Components</li>
<br />
<h3>Class Based Components</h3>
<br />
<p>
Before making class based component we need to inherit functions
from <color>React.Component</color> and this can be done with
<color>extends,</color> like this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
class Cat extends React.Component {
render() {
return <h1>Meow</h1>;
}
}
</code>
</pre>
<br />
<br />
<p>
it also requires a <color>render</color> method which returns
HTML.
</p>
<br />
<h3>Function Based Components</h3>
<br />
<p>
In function it's simpler, we just need to return the HTML, like
this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
function Cat() {
return <h1>Meow</h1>;
}
</code>
</pre>
<br />
<br />
<p>
<b>Note:</b>Component's name must start with uppercase letter.
</p>
<br />
<h3>Rendering a Component</h3>
<br />
<p>
We made a component, now we want to render/use it. Syntax for
using a component is:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
<ComponentName />
</code>
</pre>
<br />
<br />
<h3>Components in Files</h3>
<br />
<p>
To have less mess inside main file(with all the components in the
same file) and to resuse components on different pages, we have to
make them separately. So that we can just import them in any file
and use them!
<br />
For that we will just make a new file called
<color>Cat.js</color>, make class or function based component
there and <color>export default</color> that class/function! Like
this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
function Cat() {
return <h1>Meow</h1>;
}
export default Cat;
</code>
</pre>
<br />
<br />
<p><b>Note:</b> File name must start with uppercase letter.</p>
<br />
<h3>Props</h3>
<br />
<p>
As mentioned earlier, we can import the same component in
different files and use it, but maybe in different files some
changes in the component is needed. For that, we can use props!
Like this:
</p>
<br />
<h4>Component:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
function Cat(props) {
return <h1>Meow's color is {props.color}</h1>;
}
</code>
</pre>
<br />
<br />
<h4>Main file:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
<Cat color="purple" />
</code>
</pre>
<br />
<br />
</div>
<div class="notes" id="div8" style="display: none">
<h2>React Class</h2>
<br />
<h3>Class Based Components</h3>
<br />
<p>
Before making class based component we need to inherit functions
from React.Component and this can be done with extends, like this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
class Cat extends React.Component {
render() {
return <h1> Meow</h1> ;
}
}
</code>
</pre>
<br />
<br />
<p>
it also requires a render method which returns HTML.
<br />
Note: Component's name must start with uppercase letter.
</p>
<br />
<h3>Component Constructor</h3>
<br />
<p>
Constructor gets called when the component is initiated. This is
where you initiate the component's properties. In React we have
states which update on page without reload. Constructor properties
are kept in state.
<br />
We also need to add super() statement, which executes the parent
component's constructor and component gets access to all the
functions of the parent component, like this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
class Cat extends React.Component {
constructor() {
super();
this.state = { color: "orange" };
}
render() {
return <h1>Meow's color is {this.state.color}</h1>;
}
}
</code>
</pre>
<br />
<br />
</div>
<div class="notes" id="div9" style="display: none">
<h2>React Props</h2>
<br />
<p>
Props are arguments passed to React components via HTML
attributes. Example:
</p>
<br />
<h4>Component:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
function Cat(props) {
return <h1>Meow's color is {props.color}</h1>;
}
</code>
</pre>
<br />
<br />
<h4>Main file:</h4>
<br />
<pre class="highlight">
<code class="language-JS">
<Cat color="purple" />
</code>
</pre>
<br />
<br />
<h4>Output:</h4>
<br />
<img src="https://cwh-full-next-space.fra1.digitaloceanspaces.com/tutorial/react-props/react-props.png"
alt="" /><br />
<br />
</div>
<div class="notes" id="div10" style="display: none">
<h2>React Events</h2>
<br />
<p>
If you have coded even a little bit in javascript, you know the
importance of events.
</p>
<br />
<h3>Events</h3>
<br />
<p>
Every HTML attribute in React is written in camelCase syntax.
Event is also an attribute. Hence, written in camelCase.
<br />
As we learnt variables, states, javascript operations are written
in curly braces {}, same is true with React event handlers too!
Like this: <color>onClick={show}</color>
</p>
<br />
<pre class="highlight">
<code class="language-JS">
<button onClick={show}>Show</button>
</code>
</pre>
<br />
<br />
<h3>Arguments in events</h3>
<br />
<p>
We can't pass arguments just like that, it will give syntax error.
First, we need to put the whole function in arrow function, like
this:
</p>
<br />
<pre class="highlight">
<code class="language-JS">
<button onClick={ ()=>show('true')}>Show</button>
</code>
</pre>
<br />
<br />
<h3>React Event Object</h3>
<br />
<p>Event handler can be provided to the function like this:</p>
<br />
<pre class="highlight">
<code class="language-JS">
<button onClick={ (event)=>show('true', event) }>Show</button>
</code>
</pre>
<br />
<br />
</div>
<div class="notes" id="div11" style="display: none">
<h2>React Conditional</h2>
<br />
<p>
One of the best thing in React is in React we can conditionally
render elements/components!
</p>
<br />
<h3>&& Operator</h3>
<br />
<p>This is one of the way to conditionally render:</p>
<br />
<pre class="highlight">
<code class="language-JS">
function App() {
const loading = true;