React.js

 

Mar 2018, DEVUGZG, @vekzdran

A VERY          SIMPLE 101 GUIDE

...that will persuade you(r dev team) to start using it!

PRESENTER

VEDRAN MANDIć
@vekzdran

MCT
MCSD: Web Apps
.NET Dev(il)
JS LOVER
@FIVENYC

PRESENTATION Agenda

>98%

  • how it looks

  • what it is? + philosophy

  • the data(flow)

  • the lifecycle

  • the virtual DOM

  • recap with pros/cons

???%

  • demo & questions

included

  • jokes, sarcasm and 😀

  • one intentional bug 🐛

React.js fact check:

  • browser UI front-end lib developed by Facebook
  • Maintained publicly on GitHub
  • Used by Facebook, Instagram, AirBnB, Netflix...
  • A declarative, efficient, and flexible JS library for building browser UIs
  • First release Mar 2013
  • Current latest version is 16.2, released on Nov 2017
  • MIT licensed from 15.6 version

http://stateofjs.com/2016/introduction/

n <=  10000

http://stateofjs.com/2017/introduction/

n <=  10000

IT MUST BE .JS MAGIC ...

 

var React = require("react");
var createReactClass = require("create-react-class");
var Link = require("react-router").Link;
var SearchBox = require("../components/SearchBox.js");

var Header = createReactClass({
    render: function() {
        return (
            <div className="header">
                <Link to="/"> 
                    <h1>Weather App</h1>
                </Link>
                <SearchBox className="searchBoxSmall" />
            </div>
        );
    }
});
// CommonJS module approach
module.exports = Header;

... possibly even worse 🔮witchcraft ✨than Angular 2, 4 and 5

Well... IT's just javascript...

 

render: function() {
            // the <div>
    return React.createElement("div", {className: "header"}, 
        [
            // the <Link> recursively calls React.createElement in itself
            React.createElement(Link, {to: "/"}, 

                // the <h1>
                React.createElement("h1", null, "Weather App")), 
            
            // the <SearchBox>
            React.createElement(SearchBox, {className: "searchBoxSmall"}, null)  
        ]
    );
}

... syntactic sugar known as JSX

... that transforms to JavaScript!

fb/react/docs/jsx-in-depth.html

ECMASCRIPT 6

 

import React, { Component } from "React";
import { Link } from "react-router";
import SearchBox from "../components/SearchBox.js";

class Header extends Component {
    render() {
        return (
            <div className="header">
                <Link to="/"> 
                    <h1>Weather App</h1>
                </Link>
                <SearchBox className="searchBoxSmall" />
            </div>
        );
    }
}

export default Header;

... basically the standard for writing (any JavaScript app) React apps

ES6 transpiles into ES5/4/3 standards with e.g. Babel Transpiler

A jsx TL;DR
 

"JSX is like a healthy vegetable 🥕 that tastes like decadent chocolate 🍰 cake. You feel guilty, but it’s good for you."


Eric Elliot

medium.com/javascript-scene/jsx-looks-like-an-abomination

oh Modern JavaScript ...

... (╯°□°) ╯︵ ┻━┻

bit.ly/top-js-2018

airbnb.com/isomorphic-javascript-future-web-apps

NodeJS, npm, yarn, Babel transpiler, TypeScript, Webpack, rollup, Headless Chrome, LightHouse...

Chrome updates every 3 minutes... why is Addy Osmani doing this?

...HTML in .JS(X)?! 😨

return (
   <BattleAlert gameId={this.props.gameId}>
     <h1>Hello {username}, welcome to: {this.props.gameName}</h1>

     <ConfirmBattle 
        isLoading={this.state.isLoading}
        onInitiateBattle={this.handleInitiateBattle} />
   </BattleAlert>
);

...AHH, A(nother) {TEMPLATING} ENGINE!

...TON OF STUFF* DECLARED and (data)bound IN 1 FILE!?

please again... W'at is this!? :)

SEPARATION OF CONCERnS?

DO YOU EVEN (a bit)?

¯\_(ツ)_/¯

yes, SEPARATION OF... concerns and

SELF CONTAINED COMPONENTS

...concerNs are INDEED separated

  • It's "just" (a) JavaScript (view library by Facebook)
  • It's the V in MVC, but no models & no controllers
  • Components are the building blocks
  • Plain JS + JSX syntax + Virtual DOM

SO WHAT IS REACT ... ?

... it's like Lego, but with components!

fb/Thinking in React!

  • All it does is render and delegate events.
  • It knows the data it needs to render.
  • It knows when to render it (when the data changes).
  • It knows how to render it efficiently. ​

- E. Elliot

It's
Just

efficient
rendering ✏️

And WHY COMPONENTS ?

...because they are:
 

  • isolated
  • composable
  • testable
  • reusable
  • maintainable

UI components example again

hmm... NO MODELS, BUT WHERE's DATA?

  • Traditional 2-way bindings, nope
  • Data flows in 1-way
  • Parent component sends to Child(ren)
  • Props and State...

-bind="text: starDate"

Props PASSES DATA* down...

...to child components

import PrettyPrint from "./PrettyPrint";

var Writer = React.createReactClass({
    render: function () {
        return (
            <PrettyPrint text="Foo... Bar!" id={this.props.id} /> 
        );
    }
});

this.props is immutable

*also means functions, i.e. events

var PrettyPrint = createReactClass({
    render: function() {
        return (
            <p id={this.props.id} className="aPrettyParagraph">
                {this.props.text}
            </p>
        );
    }
});

#REMINDER #neverforget

...JSX is just a bunch of .js nested React.createElement() calls

STATE IS MUTABLE

USING STATE Is optional...

var PrintRandomNumber = createReactClass({

    setRandomNumber: function() {
        // changing state will fire render()
        this.setState({ number: Math.random() });
    }

    render: function () {
        return <PrettyPrint text="{this.state.number}" />;
    }
});
// This a 'Stateless Functional Component'
// Pure functional transformation of input, with zero boilerplate. 
var ICanOnlyRenderWithProps = function(props) {
    return (
        <p id={props.id} className="statlessPrettyParagraph">
            {this.props.text}
        </p>
    );
};

mutating state will fire render() and all child render() methods

tylermcginnis/functional-components-vs-stateless-functional-components-vs-stateless-components

DID you notice the bug? 🐛

TAKE CARE OF HOW YOU PASS (which) value (TYPE) to props...

var PrintRandomNumber = createReactClass({

    setRandomNumber: function() {
        // changing state will fire render()
        this.setState({ number: Math.random() });
    }

    render: function () {
        return <PrettyPrint text="{this.state.number}" />;
    }
});

ahm... also getInitialState() is missing :)

component life

MOUNT -> update -> UNMOUNT

Mounting (component mounts DOM):

Updating (state mutates or new props come):

Unmounting:

getDefaultProps() -> getInitialState() -> componentWillMount()

render() -> children component(s) lifecycle

componentDidMount()

componentWillReceiveProps() -> shouldComponentUpdate() - >componentWillUpdate()

render() -> children component(s) lifecycle

componentDidUpdate()

componentWillUnmount() -> children component(s) lifecycle

Instances destroyed for GC

gitbooks.io/react-indepth/content/life_cycle/lifecycle_methods_overview

COMPARED TO GOOD Ol' CONTROL life

MOUNT -> update -> UNMOUNT

Mounting:

Updating (on data change):

Unmounting:

  1. getInitialState() -> onLoad
  2. render() -> onRefreshUI + run nested control events
  3. componentDidMount() -> onAfterUIRefreshedFirstTime
  1. shouldComponentUpdate() - > onBeforeRefreshUI
  2. render() -> onRefreshUI + nested control events
  3. componentDidUpdate() -> onAfterRefreshUI
  1. componentWillUnmount() -> onUnload + nested control events

virtual dom

to solve the problems of the original dom

  • a HTML DOM abstraction
  • light and deattached from browser specif.
  • does not deal with drawing stuff and UI
     
  • React updates vDOM
  • vDOM updates DOM only for diffs!
  • efficient thanks to good diff algos
  • a single top level event listener

fb/react/docs/reconciliation.html

Don't you know HTML dom is ALSO an abstraction ? 💥

reactkungfu.com/the-difference-between-virtual-dom-and-dom

It's so complex and cool - South Park s14e10

REGULAR dom anybody?

SRC: https://www.huffingtonpost.com/2014/04/04/american-forests-big-tree_n_5094798.html?slideshow=true#gallery/314956/26

But what's the matter with THE normal dom? 🌳

  • When it grows... 🔥 traversing it becomes very slow
  • SPAs these days, a ton of divs...
  • abusing $(".getMAGIC_STRINGNode")🔥 ...all the nodes
  • a ton of event listeners, try finding & editing one, memory!?
  • data-mySuperDataInDom* !? (admit you've done this 💩)

HTML DOm bad keypoints

  • hard to manage
  • inefficient

that React + vDOM solve

LEt's RECAP

PRO

CONTRA

  • declarative (JSX) + plain ES6+
  • no framework specific magic
  • just the V of MVC
  • Separation of C/SCC
  • efficient vDOM
  • functional style is a +
  • easy to learn!!

  • React + Redux: < 42kB

  • TypeScript/Flow

  • pluggable on any page

  • E2E test frameworks

  • will not play nice with other existing libs like DOM and $ (but portals!)
  • optimize rerendering
  • store state management...
  • a dev philosophical shift
  • team knowledge dep.
  • split front/back arch.
  • server rendering -> SEO, general issue of PWA

Apples VS Orangutans?

medium.com/angular-2-versus-react-there-will-be-blood

⚛ Where 👓should I START LEARNING? 📚

https://www.codecademy.com/learn/react-101
 

https://reactforbeginners.com/
 

https://reactjs.org/docs/hello-world.html
 

🔥 https://tylermcginnis.com/courses/

ReactDOM.render(<DevUgZgDemo />, rootEl);

THX + Q&A 

http://bit.ly/react-dead-simple​