Hi, I am Li Hau

from Shopee!! 😀 

Facilitators

https://slides.com/tanhauhau/react

Introduction to React and Redux

Getting Started

 

https://nodejs.org/en/

JavaScript runtime built on Chrome's V8 JavaScript Engine

> node my-code.js

 

node package manager

{
  "name": "my-awesome-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "react": "^16.5.2",
    "react-dom": "^16.5.2",
    "react-scripts": "1.1.5"
  }
}
package.json
> npm install

create-react-app

npx  create-react-app  my-app-name

http://bit.ly/nus-hackers-react-dev-tools

http://bit.ly/nus-hackers-create-react-app

jsx syntax

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  <div className="red">foo bar</div>,
  document.getElementById('root')
);

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  React.createElment('div', { className: 'red' }, 'foo bar'),
  document.getElementById('root')
);

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  <div className="red">foo bar</div>,
  document.getElementById('root')
);

babel-plugin-transform-react-jsx

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  <div className="red">foo bar</div>,
  document.getElementById('root')
);

import React from 'react';
import ReactDOM from 'react-dom';

const name = 'Li Hau';

<div className="red">{ name }</div>;

JavaScript expression within {}

import React from 'react';
import ReactDOM from 'react-dom';

const elem = <div className="red">foo bar</div>;

ReactDOM.render(elem, document.getElementById('root'));

JSX is a JavaScript expression itself

import React from 'react';
import ReactDOM from 'react-dom';

const elem = (
  <div>
    <h1>Hello World</h1>
    <p>Shopee</p>
  </div>
);

ReactDOM.render(elem, document.getElementById('root'));

JSX tag may contain children

import React from 'react';
import ReactDOM from 'react-dom';

const elem = <input type="input" />;

ReactDOM.render(elem, document.getElementById('root'));

JSX tag can be without children

import React from 'react';
import ReactDOM from 'react-dom';

const elem = <div className="red">foo bar</div>;

ReactDOM.render(elem, document.getElementById('root'));

class → className

for → htmlFor

 

camelCase

tabindex → tabIndex​

maxlength → maxLength

...

 

dangerouslySetInnerHTML

https://reactjs.org/docs/dom-elements.html

import ReactDOM from 'react-dom';

ReactDOM.render(element, container, [callback]);

- strings, numbers, eg: 'text', 1

- HTML elements, eg: <a />, <div />

- React Components: eg: <ProductInfo />

- Array of elements, eg: [<li />, <li />, ...]

- Fragments

http://bit.ly/nus-hackers-react-1

null, true, false renders nothing

http://bit.ly/nus-hackers-react-2

Data Model

MODEL          VIEW

- props

- state

React Component

React Stateless Component

React Stateless Component

http://bit.ly/nus-hackers-react-component

http://bit.ly/nus-hackers-component-2

props

All React components must act like pure functions with respect to their props.

--React

props is read only

state

http://bit.ly/nus-hackers-react-state

React Context

http://bit.ly/nus-hackers-react-context

React.createContext(defaultValue)



<Provider value={/* some value */}>



<Consumer>
  {value => /* render something based on the context value */}
</Consumer>

How React works?

VIRTUAL DOM

props = { amount: 3 }

props = { amount: 10 }

props = { amount: 10 }

props = { amount: 3 }

props = { amount: 10 }

props = { amount: 3 }

props = { amount: 10 }

props = { amount: 3 }

div1.removeChild(button2);
div2.textContent = '10';
<div>
  <button>-</button>
  <div>10</div>
</div>
div1.removeChild(button2);
div2.textContent = '10';
<div>
  <button>-</button>
  <div>10</div>
</div>

RECONCILIATION

RENDERING

RECONCILIATION

RENDERING

- "Diffing" algorithm

- Renders

- Rendering

   - React (a.k.a. React DOM)

   - React Native

   - React VR

RECONCILIATION

ASYNC RENDERING

                              - Since React 16

                              - Code Name: React Fiber

React LifeCycle

http://bit.ly/nus-hackers-lifecycle

MOUNTING

constructor(props)

  • You must call super(props).
  • Do
    • Initialize your state  this.state = {...}
    • Bind your event handler
      • this.onClick = this.onClick.bind(this)
  • Don’t
    • this.setState
    • subscription

MOUNTING

UNSAFE_componentWillMount()

deprecating

  • Called right before render()

MOUNTING

static getDerivedStateFromProps(nextProps, prevState)

new

  • return new state based on the props

  • If return null, indicate no state update needed

  • static method

MOUNTING

componentDidMount()

  • Called right after component is mounted

  • Do

    • DOM nodes

    • Load remote data through network

    • Subscription, event listener

  • componentDidMount and componentWillUnmount works in pair

UPDATING

UNSAFE_componentWillReceiveProps(nextProps)

deprecating

  • Called before a mounted component receives new props

UPDATING

static getDerivedStateFromProps(nextProps, prevState)

new

  • return new state based on the props

  • If return null, indicate no state update needed

  • static method

UPDATING

shouldComponentUpdate(nextProps, nextState)

  • Called before a mounted component receives new props or state
  • Let React know if a component’s output is not affected by the current change in props or state
  • return false to prevent update.

UPDATING

UNSAFE_componentWillUpdate(nextProps, nextState)

deprecating

  • Called just right before a mounted component receives new props or new state

UPDATING

getSnapshotBeforeUpdate()

new

  • Invoked right before the most recently rendered output is committed to eg: the DOM

  • Any value returned by this lifecycle will be passed as parameter to componentDidUpdate()

UPDATING

componentDidUpdate(prevProps, prevState, snapshot)

  • Invoked right after updating occurs

  • Do:

    • Access updated DOM

    • Make network request if required

UNMOUNT

componentWillUnmount()

  • Invoked right before component is unmounted and destroyed

  • Do:

    • Cleanup: clear timers, cancel network request, unsubscribe listeners from componentDidMount

ERROR

componentDidCatch(error, info)

new

  • Catches error during rendering, lifecycle methods, and in constructor of whole tree under the component

  • Do:

    • Log error

    • Display fallback UI

http://bit.ly/nus-hackers-react-3

- Library to manage application state

- Created by Dan Abramov and Adrew Clark

 

Three Principles

Single Source of Truth

State is Read-Only

Changes are made with Pure Functions

(state, action) => nextState

http://bit.ly/nus-hackers-redux

http://bit.ly/nus-hackers-react-redux

http://bit.ly/nus-hackers-react-redux-app

Q & A

NUSHackers - React + Redux

By Li Hau Tan

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NUSHackers - React + Redux

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