Tweet
Tweet

Slide 1

Slide 1 text

With great power comes great React Hooks! Glenn Reyes @glnnrys

Slide 2

Slide 2 text

No content

Slide 3

Slide 3 text

No content

Slide 4

Slide 4 text

Glenn Reyes Freelance JavaScript Engineer @glnnrys

Slide 5

Slide 5 text

Let's talk components!

Slide 6

Slide 6 text

var App = React.createClass({ getInitialState: function() { return { value: '' }; }, onChange: function(event) { this.setState({ value: event.target.value }); }, render: function() { return (

{this.state.value}

); }, });

Slide 7

Slide 7 text

[GIF?]

Slide 8

Slide 8 text

React.createClass({ mixins: [ReactWindowMixins.OnResize], render: function() { const { window } = this.state; return (
current window size: {window.width}, {window.height}
); } });

Slide 9

Slide 9 text

React.createClass({ mixins: [ReactWindowMixins.OnResize], // render: function() { const { window } = this.state; return (
current window size: {window.width}, {window.he

Slide 10

Slide 10 text

No content

Slide 11

Slide 11 text

No content

Slide 12

Slide 12 text

class App extends React.Component { state = { value: '' }; onChange = event => { this.setState({ value: event.target.value }); } render() { return (

{this.state.value}

) } }

Slide 13

Slide 13 text

No content

Slide 14

Slide 14 text

const App = (props) => { const greeting = 'Hello'; return
{greeting} {props.name}!
; }

Slide 15

Slide 15 text

How do I add state to function components?

Slide 16

Slide 16 text

Container & Presentational Components

Slide 17

Slide 17 text

Container & Presentational Components DATA UI

Slide 18

Slide 18 text

class MyData extends React.Component { state = { value: '' }; onChange = event => { this.setState({ value: event.target.value }); } render() { return ( ) } } const MyUI = ({ value, onChange }) => (

{value}

)

Slide 19

Slide 19 text

class MyData extends React.Component { state = { value: '' }; onChange = event => { this.setState({ value: event.target.value }); } render() { return ( ) } } const MyUI = ({ value, onChange }) => (

{value}

) class MyData extends React.Component { state = { value: '' }; onChange = event => { this.setState({ value: event.target.value }); } render() { return ( ) } }

Slide 20

Slide 20 text

Higher Order Components!

Slide 21

Slide 21 text

const EnhancedComponent = higherOrderComponent(WrappedComponent);

Slide 22

Slide 22 text

const withInput = Component => class InputContainer extends React.Component { state = { value: '' }; onChange = event => { this.setState({ value: event.target.value }); } render() { return ( ) } } const App = withInput(({ value, onChange }) => (

{value}

))

Slide 23

Slide 23 text

hoc1(hoc2(hoc3(hoc4(Component))))

Slide 24

Slide 24 text

compose( hoc1, hoc2, hoc3, hoc4 )(Component)

Slide 25

Slide 25 text

Thank god Render Props came around!

Slide 26

Slide 26 text

class DataProvider extends React.Component { state = { data: null } componentDidMount() { fetchSomeData().then(data => this.setState({ data })); } render() { return this.props.render(data); } } (

Hello {data.name}

)}/>

Slide 27

Slide 27 text

class DataProvider extends React.Component { state = { data: null } componentDidMount() { fetchSomeData().then(data => this.setState({ data })); } render() { return this.props.render(data); } } (

Hello {data.name}

)}/> class DataProvider extends React.Component { state = { data: null } componentDidMount() { fetchSomeData().then(data => this.setState({ data })); } render() { return this.props.render(data); } }
 
 
 
 


Slide 28

Slide 28 text

class DataProvider extends React.Component { state = { data: null } componentDidMount() { fetchSomeData().then(data => this.setState({ data })); } render() { return this.props.render(data); } } (

Hello {data.name}

)}/> 
 
 
 
 
 
 
 return this.props.render(data);
 
 
 
 
 
 


Slide 29

Slide 29 text

class DataProvider extends React.Component { state = { data: null } componentDidMount() { fetchSomeData().then(data => this.setState({ data })); } render() { return this.props.render(data); } } (

Hello {data.name}

)}/> 
 
 
 
 
 
 
 
 
 
 
 
 (

Hello {data.name}

)}/>

Slide 30

Slide 30 text

class DataProvider extends React.Component { state = { data: null } componentDidMount() { fetchSomeData().then(data => this.setState({ data })); } render() { return this.props.render(data); } } (

Hello {data.name}

)}/> 
 
 
 
 
 
 
 
 
 
 
 
 data => (

Hello {data.name}

)

Slide 31

Slide 31 text

class DataProvider extends React.Component { state = { data: null } componentDidMount() { fetchSomeData().then(data => this.setState({ data })); } render() { return this.props.children(data); } } {data => (

Hello {data.name}

)}

Slide 32

Slide 32 text

https://medium.com/@jackyef/react-hooks-why-we-should-embrace-it-86e408663ad6

Slide 33

Slide 33 text

No content

Slide 34

Slide 34 text

Hooks!

Slide 35

Slide 35 text

What are React Hooks?

Slide 36

Slide 36 text

Hooks let you use state and other React features
 without writing a class!

Slide 37

Slide 37 text

Hooks let you use state and other React features
 with just function components!

Slide 38

Slide 38 text

import React, { useState } from 'react'; function Example() { const [count, setCount] = useState(0); return (

You clicked {count} times

setCount(count + 1)}> Click me
); }

Slide 39

Slide 39 text

✅ New feature as of React 16.8 ✅ Completely opt-in ✅ No breaking changes ✅ Fully backwards compatible

Slide 40

Slide 40 text

Why React Hooks?

Slide 41

Slide 41 text

Better reuse and primitive for stateful logic between components

Slide 42

Slide 42 text

class Example extends React.Component { constructor(props) { super(props); this.state = { count: 0 }; } componentDidMount() { document.title = `You clicked ${this.state.count} times`; } componentDidUpdate() { document.title = `You clicked ${this.state.count} times`; } render() { return (

You clicked {this.state.count} times

this.setState({ count: this.state.count + 1 })}> Click me
); } }

Slide 43

Slide 43 text

class Example extends React.Component { constructor(props) { super(props); this.state = { count: 0 }; } componentDidMount() { document.title = `You clicked ${this.state.count} times`; } componentDidUpdate() { document.title = `You clicked ${this.state.count} times`; } render() { return (

You clicked {this.state.count} times

this.setState({ count: this.state.count + 1 })}> Click me
); } }

Slide 44

Slide 44 text

function Example() { const [count, setCount] = useState(0); useEffect(() => { document.title = `You clicked ${count} times`; }); return (

You clicked {count} times

setCount(count + 1)}> Click me
); }

Slide 45

Slide 45 text

class FriendStatusWithCounter extends React.Component { constructor(props) { super(props); this.state = { count: 0, isOnline: null }; this.handleStatusChange = this.handleStatusChange.bind(this); } componentDidMount() { document.title = `You clicked ${this.state.count} times`; ChatAPI.subscribeToFriendStatus( this.props.friend.id, this.handleStatusChange ); } componentDidUpdate() { document.title = `You clicked ${this.state.count} times`; } componentWillUnmount() { ChatAPI.unsubscribeFromFriendStatus( this.props.friend.id, this.handleStatusChange ); } handleStatusChange(status) { this.setState({ isOnline: status.isOnline }); } // ...

Slide 46

Slide 46 text

function FriendStatusWithCounter(props) { const [count, setCount] = useState(0); useEffect(() => { document.title = `You clicked ${count} times`; }); const [isOnline, setIsOnline] = useState(null); useEffect(() => { function handleStatusChange(status) { setIsOnline(status.isOnline); } ChatAPI.subscribeToFriendStatus(props.friend.id, handleStatusChange); return () => { ChatAPI.unsubscribeFromFriendStatus(props.friend.id, handleStatusChange); }; }); // ... }

Slide 47

Slide 47 text

Hooks lets us organize logic into reusable isolated units

Slide 48

Slide 48 text

No more wrapper hell

Slide 49

Slide 49 text

DEMO TIME!

Slide 50

Slide 50 text

What will happen to React classes?

Slide 51

Slide 51 text

Nothing.

Slide 52

Slide 52 text

How will hooks affect the core concepts of React?

Slide 53

Slide 53 text

✅ Everything you already know won't change ✅ Hooks provide a more direct API props state context refs lifecycle

Slide 54

Slide 54 text

No more constructor No more bindings No more this Less code Cleaner code Learning curve Bigger React API surface Not all covered (yet) There are some rules

Slide 55

Slide 55 text

☝ Only from React functions ☝ Only on top level

Slide 56

Slide 56 text

Hooks rely on call order.

Slide 57

Slide 57 text

function Form() { // 1. Use the name state variable const [name, setName] = useState('Mary'); // 2. Use an effect for persisting the form useEffect(function persistForm() { localStorage.setItem('formData', name); }); // 3. Use the surname state variable const [surname, setSurname] = useState('Poppins'); // 4. Use an effect for updating the title useEffect(function updateTitle() { document.title = name + ' ' + surname; }); // ... }

Slide 58

Slide 58 text

// ------------ // First render // ------------ useState('Mary') // 1. Initialize name state variable with 'Mary' useEffect(persistForm) // 2. Add an effect for persisting the form useState('Poppins') // 3. Initialize surname state variable useEffect(updateTitle) // 4. Add an effect for updating the title // ------------- // Second render // ------------- useState('Mary') // 1. Read name state variable (argument ignored) useEffect(persistForm) // 2. Replace the effect for persisting the form useState('Poppins') // 3. Read surname state variable (argument ignored) useEffect(updateTitle) // 4. Replace the effect for updating the title // ...

Slide 59

Slide 59 text

// We're breaking the rule by using a Hook in a condition if (name !== '') { useEffect(function persistForm() { localStorage.setItem('formData', name); }); }

Slide 60

Slide 60 text

useState('Mary') // 1. Read name state variable (argument ignored) // useEffect(persistForm) // This Hook was skipped! useState('Poppins') // 2 (but was 3). Fail to read the surname state useEffect(updateTitle) // 3 (but was 4). Fail to replace the effect

Slide 61

Slide 61 text

useEffect(function persistForm() { // We're not breaking the first rule anymore if (name !== '') { localStorage.setItem('formData', name); } });

Slide 62

Slide 62 text

When to useReducer over useState?

Slide 63

Slide 63 text

Start with useState when building new components

Slide 64

Slide 64 text

Switch to useReducer on larger state shapes

Slide 65

Slide 65 text

How about tooling?

Slide 66

Slide 66 text

eslint-plugin-react-hooks "react-hooks/rules-of-hooks": "error", "react-hooks/exhaustive-deps": "warn",

Slide 67

Slide 67 text

No content

Slide 68

Slide 68 text

How to do I test React Hooks?

Slide 69

Slide 69 text

You don't.

Slide 70

Slide 70 text

Test the component as usual.

Slide 71

Slide 71 text

@glnnrys reactjs.org/hooks nikgraf.github.io/react-hooks github.com/rehooks/awesome-react-hooks codesandbox.io/s/github/glennreyes/hooks-demo

Slide 72

Slide 72 text

Glenn Reyes @glnnrys Thank you! reactjs.org/hooks nikgraf.github.io/react-hooks github.com/rehooks/awesome-react-hooks codesandbox.io/s/github/glennreyes/hooks-demo