React Introduction - Speaker Deck

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1 React Introduction

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2 SPEAKERS Timotius Kevin L Senior Software Development Engineer Hogiyanto Purnama L Principal Software Development Engineer

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GDP Labs Statistics as of December 2020 3 PARTNERSHIP 50+ projects 70+ clients 26 partners EXPERTISE 1,000+ years of experience 100+ won programming competition 1,400+ years of programming 21,000+ books read 38,000 weekly reports TECHNOLOGY 60+ SaaS used 150+ technologies used 320,000+ articles read INCUBATE STARTUPS COMPANY - Born Cloud-Native 9 years since founded in 2012 200+ talented employees 5 offices in 5 cities 80% engineers 20+ certified people 1600++ trainings taken

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glair.ai 5 Products and Services Consulting Service On demand talents capable of crafting customized solutions Analytics Platform An easy & intelligent way to turn your data into insights Training Center We are what we invest

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Themed Days Sharing Hard Work Continuous Learning Team Building

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7 1. What is React? 2. Why React? 3. React vs Vanilla JS 4. Main Concepts 5. Frameworks 6. Setup & Installation 7. Demo Outline

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8 What is React?

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9 What is React? ● JavaScript library for building user interfaces ● Open-source project by Facebook ● View layer in MVC

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10 Why React?

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11 Why React? ● Virtual DOM ● Component-based ● Declarative

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12 React vs Vanilla JS

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13 React vs Vanilla JS? ● How the UI is first created ● How functionality is split up across the app ● How data is stored on the browser ● How the UI is updated

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14 React vs Vanilla JS? How the UI is first created (Vanilla JS) ● index.html

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15 React vs Vanilla JS? How the UI is first created (React) ● index.html

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16 React vs Vanilla JS? How the UI is first created (React) ● index.jsx

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17 React vs Vanilla JS? How functionality is split up across the app (Vanilla JS) ● index.html

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18 React vs Vanilla JS? How functionality is split up across the app (Vanilla JS) ● grocery.js

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19 React vs Vanilla JS? How functionality is split up across the app (React) ● index.jsx

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20 React vs Vanilla JS? How data is stored on the browser (Vanilla JS) ● index.html

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21 React vs Vanilla JS? How data is stored on the browser (Vanilla JS) ● grocery.js

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22 React vs Vanilla JS? How data is stored on the browser (React) ● index.jsx

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23 React vs Vanilla JS? How the UI is updated (Vanilla JS) ● index.html

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24 React vs Vanilla JS? How the UI is updated (Vanilla JS) ● grocery.js

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25 React vs Vanilla JS? How the UI is updated (React) ● index.jsx

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26 Main Concepts

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27 Main Concepts ● JSX ● Components and Props ● State and Lifecycle ● Hooks

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28 Main Concepts JSX Why JSX? ● It's easier to describe what the UI should look like ● Embraces the fact that rendering logic is inherently coupled with other UI logic

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29 Main Concepts JSX

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30 Main Concepts JSX

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31 Main Concepts JSX

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32 Main Concepts Components and Props Rules: ● Start component names with a capital letter ● Props (properties) are read-only ● All React components must act like pure functions with respect to their props

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33 Main Concepts Components and Props ● Defining a component

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34 Main Concepts Components and Props ● Rendering a component

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35 Main Concepts Lifecycle ● Mounting instance of a component is being created and inserted into the DOM ● Updating changes to props or state ● Unmounting component is being removed from the DOM

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36 Main Concepts Lifecycle https://projects.wojtekmaj.pl/react-lifecycle-methods-diagram/

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37 Main Concepts Lifecycle class HelloWorld extends React.Component { constructor(props) { ... } componentDidMount() { ... } componentDidUpdate(prevProps) { ... } componentWillUnmount() { ... } render() { ... } }

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38 Main Concepts State Both props and state changes trigger a render update. So when would you use state? When a component needs to keep track of information between renderings, the component itself can create, update, and use state.

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39 Main Concepts State The state starts with a default value when a Component mounts class Counter extends React.Component { constructor() { super(); this.state = { count: 0 }; } render() { ... } }

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40 Main Concepts State class Counter extends React.Component { constructor() { ... } updateCount() { this.setState((prevState, props) => { return { count: prevState.count + 1 } }) } render() { return ( this.updateCount()}> Clicked {this.state.count} times ) } } The state then suffers from mutations in time (mostly generated from user events)

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41 Main Concepts Hooks Hooks are a new addition in React 16.8. They let you use state and other React features without writing a class. function Example(props) { // You can use Hooks here! return

}

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42 Main Concepts Hooks A Hook is a special function that lets you “hook into” React features ● useState ● useEffect ● useCallback ● useMemo

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43 Main Concepts Hooks function Counter() { // Declare a new state variable, which we'll call "count" const [count, setCount] = useState(0); return ( setCount(count + 1)}> Clicked {count} times ) } ● useState call it inside a function component to add some local state to it

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44 Main Concepts Hooks function Counter() { // Similar to componentDidMount and componentDidUpdate: useEffect(() => { // Update the document title using the browser API document.title = `You clicked ${count} times` }, [count]) return ( setCount(count + 1)}> Clicked {count} times ) } ● useEffect wrap a function that contains imperative, possibly effectful code

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45 Main Concepts Hooks function Counter() { const alertCount = useCallback(() => { alert(`You clicked ${count} times`) }, [count]) return ( <> setCount(count + 1)}> Clicked {count} times > ) } ● useCallback returns a memoized callback that only changes if one of the dependencies has changed

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46 Main Concepts Hooks function Counter() { const memoizedValue = useMemo(() => { // computeExpensiveValue is a function with heavy calculation return computeExpensiveValue(count) }, [count]) return ( <>

Computation result: {memoizedValue}

setCount(count + 1)}> Clicked {count} times > ) } ● useMemo returns a memoized value, it only recomputes when one of the dependencies has changed

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47 Frameworks

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48 Frameworks create-react-app Gatsby NextJS

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49 Setup & Installation

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50 Setup & Installation ● Static HTML File ● create-react-app

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51 Setup & Installation Static HTML File

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52 Setup & Installation Static HTML File

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53 Demo

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54 What's Next? ● Typescript ○ Official Documentation ○ React + Typescript Cheatsheets ● Styling ○ material-ui ○ tailwindcss ○ styled-components ● Static Code Analysis ○ eslint ● Testing ○ jest ○ react-testing-library

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55 References ● React JS ● React Tutorial: An Overview and Walkthrough ● React v/s Vanilla JS - When to use what? ● React vs. Plain JavaScript

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