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WHAT THE v...DOM? @stefanjudis

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STEFAN JUDIS @stefanjudis www.stefanjudis.com stefan.judis@contentful.com

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2013

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"Super fast and revolutionary because of the virtual DOM
 and JSX." MAGIC!

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THERE IS NO MAGIC IN CODE!

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SOMETIMES
 IT FEELS 
 LIKE MAGIC

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TAKE A BREAK!

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Matthias

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IMPERATIVE

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Go out of the door and turn left.
 Get on Frankfurter Allee until you get to the Proskauer Straße.
 Go left at the park. Go to the end of the park.
 My house is #22.

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The imperative programming paradigm uses statements 
 that change a program's state. “

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DECLARATIVE

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My address is Berlin, Friedrichshain.

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“ The declarative programming paradigm expresses the logic of a computation without describing its control flow.

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Imperative function double (arr) { let results = []; for (let i = 0; i < arr.length; i++){ results.push(arr[i] * 2); } return results; } Declarative function double (arr) { return arr.map((item) => item * 2); }

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INTERFACES

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const $btn = document.getElementById('btn'); $btn.addEventListener('click', _ => { $btn.classList.toggle('is-highlighted'); $btn.innerText = $btn.innerText === 'Highlight me!' ? 'Please stop!' : 'Highlight me!'; }); Imperative UI

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Declarative UI { highlighted ? 'Please stop!': 'Highlight me!' }

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{ highlighted ? 'Please stop!': 'Highlight me!' }

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export default class App extends Component { ... render(props, { highlighted }) { return ( { highlighted ? 'Please stop!': 'Highlight me!' } ); } } codesandbox.io/s/rwjol2n3op

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export default class App extends Component { ... render(props, { highlighted }) { return ( { highlighted ? 'Please stop!': 'Highlight me!' } ); } } codesandbox.io/s/rwjol2n3op THAT'S NOT JAVASCRIPT!?

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CODE TRANSFORMS

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! & ? PARSE ! ~ ? TRANSFORM GENERATE

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./example/input.js const year = (new Date()).getFullYear(); const msg = `:tada: Frontend Con ${year}! :tada:`; console.log(msg);

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babeljs.io

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PARSE with Babylon

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const {parse} = require('babylon'); const code = ` const year = (new Date()).getFullYear(); const msg = ':tada: Frontend Con ${year}! :tada:'; console.log(msg); `; const ast = parse(code); ./my-own-code-transform/index.js

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AST ( Abstract Syntax Tree )

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“In computer science, an abstract syntax tree (AST), [...], is a tree representation of the abstract syntactic structure of source code written in a programming language.

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{ "type": "Program", "start": 0, "end": 105, "loc": { "start": { "line": 1, "column": 0 }, "end": { "line": 3, "column": 17 } } }

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{ "type": "VariableDeclaration", "start": 0, "end": 40, "loc": { "start": { "line": 1, "column": 0 }, "end": { "line": 1, "column": 40 } }, "declarations": [...], "kind": "const" }

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{ "type": "ExpressionStatement", "start": 88, "end": 105, "loc": { "start": { "line": 3, "column": 0 }, "end": { "line": 3, "column": 17 } }, "expression": {...} }

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const msg = `:tada: Frontend Con ${year}! :tada:`; ./example/input.js

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const msg = `:tada: Frontend Con ${year}! :tada:`; ./example/input.js VariableDeclaration

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./example/input.js VariableDeclarator const msg = `:tada: Frontend Con ${year}! :tada:`; VariableDeclaration

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./example/input.js VariableDeclarator const msg = `:tada: Frontend Con ${year}! :tada:`; VariableDeclaration Identifier

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./example/input.js VariableDeclarator const msg = `:tada: Frontend Con ${year}! :tada:`; VariableDeclaration Identifier TemplateLiteral

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./example/input.js VariableDeclarator const msg = `:tada: Frontend Con ${year}! :tada:`; VariableDeclaration Identifier TemplateLiteral TemplateElement

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./example/input.js VariableDeclarator const msg = `:tada: Frontend Con ${year}! :tada:`; VariableDeclaration Identifier TemplateLiteral TemplateElement Identifier

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./example/input.js VariableDeclarator const msg = `:tada: Frontend Con ${year}! :tada:`; VariableDeclaration Identifier TemplateLiteral TemplateElement TemplateElement Identifier

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astexplorer.net

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ASTs are everywhere

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astexplorer.net

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ctfl.io/asts-in-graphql

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TRANSFORM with @babel/traverse

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VISITOR PATTERN ( design pattern described by the "Gang of Four" )

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const {parse} = require('babylon'); const code = `...`; const ast = parse(code); ./my-own-code-transform/index.js

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const {parse} = require('babylon'); const {default: traverse} = require('@babel/traverse'); const code = `...`; const ast = parse(code); traverse(ast, { enter ({node}) { if (node.type === 'TemplateElement') { node.value.raw = node.value.raw.replace(/:tada:/g, '\u{1F389}'); } } }); ./my-own-code-transform/index.js

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const {parse} = require('babylon'); const {default: traverse} = require('@babel/traverse'); const code = `...`; const ast = parse(code); traverse(ast, { enter ({node}) { if (node.type === 'TemplateElement') { node.value.raw = node.value.raw.replace(/:tada:/g, '\u{1F389}'); } } }); ./my-own-code-transform/index.js

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GENERATE with @babel/generator

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const {parse} = require('babylon'); const {default: traverse} = require('@babel/traverse'); const code = `...`; const ast = parse(code); traverse(ast, { enter (path) { /* ... */ } }); ./my-own-code-transform/index.js

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./my-own-code-transform/index.js const {parse} = require('babylon'); const {default: traverse} = require('@babel/traverse'); const {default: generate} = require('@babel/generator'); const code = `...`; const ast = parse(code); traverse(ast, { enter (path) { /* ... */ } }); console.log(generate(ast).code);

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BABEL PLUGIN

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./lib/index.js export default function () { return { visitor: { TemplateElement({node}) { node.value.raw = node.value.raw.replace( /:tada:/g, '\u{1F389}' ); } } }; }

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export default function () { return { visitor: { TemplateElement({node}) { node.value.raw = node.value.raw.replace( /:tada:/g, '\u{1F389}' ); } } }; } ./lib/index.js

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export default function () { return { visitor: { TemplateElement({node}) { node.value.raw = node.value.raw.replace( /:tada:/g, '\u{1F389}' ); } } }; } ./lib/index.js

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export default function () { return { visitor: { TemplateElement({node}) { node.value.raw = node.value.raw.replace( /:tada:/g, '\u{1F389}' ); } } }; } ./lib/index.js

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github.com/jamiebuilds/babel-handbook

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JSX ( just another transform )

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babel-plugin-transform-react-jsx const App = () => { return

:tada: Frontend Con 2018! :tada:

; };

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const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; babel-plugin-transform-react-jsx ReturnStatement

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const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; babel-plugin-transform-react-jsx ReturnStatement JSXElement

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const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; babel-plugin-transform-react-jsx ReturnStatement JSXElement JSXOpeningElement

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const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; babel-plugin-transform-react-jsx ReturnStatement JSXElement JSXOpeningElement JSXText

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const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; babel-plugin-transform-react-jsx ReturnStatement JSXElement JSXOpeningElement JSXText JSXClosingElement

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const App = () => { return React.createElement( "h1", null, "! Frontend Con 2018! !" ); }; const App = () => { return

:tada: Frontend Con 2018! :tada:

; };

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const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; const App = () => { return React.createElement( "h1", null, "! Frontend Con 2018! !" ); };

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const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; const App = () => { return React.createElement( "h1", null, "! Frontend Con 2018! !" ); }; REACT?

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/* @jsx heroify */ const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; babel-plugin-transform-react-jsx

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/* @jsx heroify */ const App = () => { return heroify( "h1", null, "! Frontend Con 2018! !" ); }; /* @jsx heroify */ const App = () => { return

:tada: Frontend Con 2018! :tada:

; };

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/* @jsx h */ const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; /* @jsx h */ const App = () => { return h( "h1", null, "! Frontend Con 2018! !" ); };

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/* @jsx h */ import {h} from 'preact'; const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; /* @jsx h */ import {h} from 'preact'; const App = () => { return h( "h1", null, "! Frontend Con 2018! !" ); };

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/* @jsx h */ import {h} from 'preact'; const App = () => { return

:tada: Frontend Con 2018! :tada:

; }; /* @jsx h */ import {h} from 'preact'; const App = () => { return h( "h1", null, "! Frontend Con 2018! !" ); }; JSX is only one option

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vue-template-explorer.now.sh

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vue-template-explorer.now.sh You don't need a complex build setup

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You don't need JSX

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You don't need JSX /* Preact 8.2.9 */ !function () { "use strict"; function e() { } function ...

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You don't need JSX /* Preact 8.2.9 */ !function () { "use strict"; function e() { } function ... const { h, render } = window.preact;

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You don't need JSX /* Preact 8.2.9 */ !function () { "use strict"; function e() { } function ... const { h, render } = window.preact; render( h('h1', {class: 'headline-1'}, '! Frontend Con 2018! !'), document.body );

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reactjs.org/docs/react-without-jsx.html

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github.com/developit/htm

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h()?

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github.com/hyperhype/hyperscript

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const h = (nodeName, attributes, ...children) => {}; ./our-hyperscript.js

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const h = (nodeName, attributes, ...children) => { const el = document.createElement(nodeName); return el; }; ./our-hyperscript.js

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const h = (nodeName, attributes, ...children) => { const el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } return el; }; ./our-hyperscript.js

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for (let key in attributes) { el.setAttribute(key, attributes[key]); } ./our-hyperscript.js

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for (const key of Object.keys(attributes)) { el.setAttribute(key, attributes[key]); } ./our-hyperscript.js

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for (const [key, value] of Object.entries(attributes)) { el.setAttribute(key, value); } ./our-hyperscript.js

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ctfl.io/fun-with-enumeration

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const h = (nodeName, attributes, ...children) => { const el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } return el; }; ./our-hyperscript.js

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const h = (nodeName, attributes, ...children) => { const el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } children.forEach(child => { if (typeof child === 'string') { el.appendChild(document.createTextNode(child)); } else { el.appendChild(child); } }); return el; }; ./our-hyperscript.js

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import h from './our-hyperscript.js'; const App = () => { return h( "h1", null, "! Frontend Con 2018! !" ); }; console.log('App()', App()); ./app.js

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import h from './our-hyperscript.js'; const App = () => { return h( "h1", null, "! Frontend Con 2018! !" ); }; console.log('App()', App()); ./app.js

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const App = () => { return h( "h1", null, "! Frontend Con 2018! !" ); }; ./app.js

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const App = (props) => { const {list} = props; return h('div', {class: 'app'}, h('h1', null, '! Frontend Con 2018! !'), h('ul', null, ...list.map(item => h('li', null, item)) ) ); }; ./app.js

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./app.js const App = (props) => { const {list} = props; return (
,

! Frontend Con 2018! !

    {...list.map(item =>
  • {item}
    • )}
); };

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const App = (props) => { const {list} = props; return h('div', {class: 'app'}, h('h1', null, '! Frontend Con 2018! !'), h('ul', null, ...list.map(item => h('li', null, item)) ); ); }; ./app.js

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const App = (props) => {...}; ./app.js

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let currentApp; const App = (props) => {...}; const render = (state) => { const newApp = App(state); if (currentApp) { document.body.replaceChild(newApp, currentApp); } else { document.body.appendChild(newApp); } currentApp = newApp; }; ./app.js

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let currentApp; const App = (props) => {...}; const render = (state) => {...}; ./app.js

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let currentApp; const App = (props) => {...}; const render = (state) => {...}; const state = { list: [ '"', '#', '$', '%', '&', ''', '(', ')', '*', '+' ] }; ./app.js

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let currentApp; const App = (props) => {...}; const render = (state) => {...}; const state = { list: [ '"', '#', '$', '%', '&', ''', '(', ')', '*', '+' ] }; render(state); ./app.js

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NICELY DECLARATIVE

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let currentApp; const App = (props) => {...}; const render = (state) => {...}; const state = {...}; render(state); ./app.js

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let currentApp; const App = (props) => {...}; const render = (state) => {...}; const state = {...}; render(state); setInterval(_ => { state.list = [ ...state.list, getRandomItemFromArray(state.list) ]; render(state); }, 1000); ./app.js

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A LOT OF WORK TO DO

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“We want to render components and have them updated only when data changes - that's where the power of vDOM diffing shines.

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vWHAT?

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Virtual DOM on GitHub

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Features Community Performance Which one should I use? DX Documentation Ecosystem Stability

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Features Community Performance Which one should I use? DX Documentation Ecosystem Stability There are always trade-offs...

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h()

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const h = (nodeName, attributes, ...children) => { const el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } children.forEach(child => { if (typeof child === 'string') { el.appendChild(document.createTextNode(child)); } else { el.appendChild(child); } }) return el; } ./our-vdom.js

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./our-vdom.js const h = (nodeName, attributes, ...children) => { return {nodeName, attributes, children}; } h(...) → virtual DOM nodes

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const App = (props) => { const {list} = props; return h('div', {class: 'app'}, h('h1', null, '! Frontend Con 2018! !'), h('ul', null, ...list.map(item => h('li', null, item)) ) ); }; ./app.js

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const App = (props) => {...}; ./app.js { "nodeName": "div", "attributes": { "class": "app" }, "children": [ { "nodeName": "h1", "attributes": null, "children": ["! Frontend Con 2018! !"] }, { "nodeName": "ul", "attributes": null, "children": [ { "nodeName": "li", "attributes": null, "children": ["""] },

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const renderNode = (vnode) => { } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); el = document.createElement(nodeName); } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } (children || []).forEach(c => el.appendChild(renderNode(c))); return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } (children || []).forEach(c => el.appendChild(renderNode(c))); return el; } ./our-vdom.js

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let currentApp; const App = (props) => {...}; const render = (state) => { const newApp = App(state); if (currentApp) { document.body.replaceChild(newApp, currentApp); } else { document.body.appendChild(newApp); } currentApp = newApp; }; ./app.js

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let currentApp; const App = (props) => {...}; const render = (state) => { const newApp = renderNode(App(state)); if (currentApp) { document.body.replaceChild(newApp, currentApp); } else { document.body.appendChild(newApp); } currentApp = newApp; }; ./app.js

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MORE CONTROL

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COMPONENT RENDERING

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./app.js const App = ({list}) => { return h('div', {class: 'app'}, h('h1', null, '! Frontend Con 2018! !'), h('ul', null, ...list.map(item => h('li', null, item)) ); ); };

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./app.js class App { constructor () { this.state = { list: ['"', '#', '$', ...] }; } render (props, state) { const {list} = state; return h('div', {class: 'app'}, h('h1', null, '! Frontend Con 2018! !'), h('ul', null, ...list.map(item => h('li', null, item)) ) ); } }

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./app.js class App { constructor () { this.state = { list: ['"', '#', '$', ...] }; } render (props, {list}) { return h('div', {class: 'app'}, h('h1', null, '! Frontend Con 2018! !'), h('ul', null, ...list.map(item => h('li', null, item)) ) ); } }

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } (children || []).forEach(c => el.appendChild(renderNode(c))); return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { el = document.createElement(nodeName); for (let key in attributes) { el.setAttribute(key, attributes[key]); } (children || []).forEach(c => el.appendChild(renderNode(c))); } return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { // ... } return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { // ... } else if (typeof nodeName === 'function') { // ... } return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { // ... } else if (typeof nodeName === 'function') { // ... } return el; } ./our-vdom.js overreacted.io/how-does-react-tell-a-class-from-a-function/

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { // ... } else if (typeof nodeName === 'function') { // ... } return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { // ... } else if (typeof nodeName === 'function') { const component = new nodeName(attributes); el = renderNode(component.render(component.props, component.state)); component.base = el; } return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { // ... } else if (typeof nodeName === 'function') { const component = new nodeName(attributes); el = renderNode(component.render(component.props, component.state)); component.base = el; } return el; } ./our-vdom.js

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const renderNode = (vnode) => { let el; const {nodeName, attributes, children} = vnode; if (vnode.split) return document.createTextNode(vnode); if (typeof nodeName === 'string') { // ... } else if (typeof nodeName === 'function') { const component = new nodeName(attributes); el = renderNode(component.render(component.props, component.state)); component.base = el; } return el; } ./our-vdom.js A COMPONENT HOLDS A DOM REFERENCE

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setState()

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; } render (props, {list}) { return h('div', {class: 'app'}, h('h1', null, '! Frontend Con 2018! !'), h('ul', null, ...list.map(item => h('li', null, item)) ) ); } }

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; } render (props, {list}) {...} }

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } render (props, {list}) {...} }

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } setState(state) { this.state = Object.assign(this.state, state); renderComponent(this); } render (props, {list}) {...} }

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } setState(state) { this.state = Object.assign(this.state, state); renderComponent(this); } render (props, {list}) {...} }

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renderComponent() , , , , , ! ! - . . / /

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const renderComponent = (component) => { }; ./our-vdom.js

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const renderComponent = (component) => { const oldBase = component.base; }; ./our-vdom.js

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const renderComponent = (component) => { const oldBase = component.base; component.base = renderNode( component.render(component.props, component.state) ); }; ./our-vdom.js

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const renderComponent = (component) => { const oldBase = component.base; component.base = renderNode( component.render(component.props, component.state) ); oldBase.parentNode.replaceChild(component.base, oldBase); }; ./our-vdom.js

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const renderComponent = (component) => { const oldBase = component.base; component.base = renderNode( component.render(component.props, component.state) ); oldBase.parentNode.replaceChild(component.base, oldBase); } COMPONENTS 
 RENDER 
 AUTONOMOUSLY ./our-vdom.js

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render() render() setState({...}) renderComponent(this) render() render() document.body APP SIDEBAR WIDGET MAIN SLIDER TABS SIDEBAR WIDGET SLIDER TABS

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renderComponent(this) render() LIST document.body APP LIST setInterval(...) setState({...})

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document.body APP ... ... ...

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DIFFING

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const renderComponent = (component) => { const oldBase = component.base; component.base = renderNode( component.render(component.props, component.state) ); oldBase.parentNode.replaceChild(component.base, oldBase); }; ./our-vdom.js

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const renderComponent = (component) => { const oldBase = component.base; component.base = renderNode( component.render(component.props, component.state) ); oldBase.parentNode.replaceChild(component.base, oldBase); }; DOM ./our-vdom.js

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const renderComponent = (component) => { const oldBase = component.base; component.base = renderNode( component.render(component.props, component.state) ); oldBase.parentNode.replaceChild(component.base, oldBase); }; virtual DOM ./our-vdom.js

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{ nodeName: 'div', attributes: { key: 'value' }, children: [ 'text node' ] } Element( nodeName: 'div', attributes: { getItem('key'), setItem('key', 'value') }, childNodes: [ TextNode('text node') ] ) DOM virtual DOM ./our-vdom.js

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const renderComponent = (component) => { const oldBase = component.base; component.base = renderNode( component.render(component.props, component.state) ); oldBase.parentNode.replaceChild(component.base, oldBase); }; ./our-vdom.js

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const renderComponent = (component) => { }; ./our-vdom.js

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const renderComponent = (component) => { const rendered = component.render( component.props, component.state ); }; ./our-vdom.js

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const renderComponent = (component) => { const rendered = component.render( component.props, component.state ); diff(component.base, rendered); }; ./our-vdom.js

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const renderComponent = (component) => { const rendered = component.render( component.props, component.state ); component.base = diff(component.base, rendered); }; ./our-vdom.js

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const diff = (dom, vnode) => { }; ./our-vdom.js

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const diff = (dom, vnode) => { const newDom = renderNode(vnode); dom.parentNode.replaceChild(newDom, dom); return newDom; }; ./our-vdom.js

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const diff = (dom, vnode) => { const hasNewKids = dom.childNodes.length !== vnode.children.length; if (hasNewKids) { } else { const newDom = renderNode(vnode); dom.parentNode.replaceChild(newDom, dom); return newDom; } }; ./our-vdom.js

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const diff = (dom, vnode) => { const hasNewKids = dom.childNodes.length !== vnode.children.length; if (hasNewKids) { dom.appendChild( renderNode(vnode.children[vnode.children.length - 1]) ); return dom; } else { const newDom = renderNode(vnode); dom.parentNode.replaceChild(newDom, dom); return newDom; } }; ./our-vdom.js

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ONLY TOUCH WHAT CHANGED

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DOM { nodeName: 'div', attributes: { key: 'value' }, children: [ 'text node' ] } Element( nodeName: 'div', attributes: { getItem('key'), setItem('key', 'value') }, childNodes: [ TextNode('text node') ] ) virtual DOM

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DOM { nodeName: 'div', attributes: { key: 'value' }, children: [ 'text node' ] } Element( nodeName: 'div', attributes: { getItem('key'), setItem('key', 'value') }, childNodes: [ TextNode('text node') ] ) virtual DOM

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DOM { nodeName: 'div', attributes: { key: 'value' }, children: [ 'text node' ] } Element( nodeName: 'div', attributes: { getItem('key'), setItem('key', 'value') }, childNodes: [ TextNode('text node') ] ) virtual DOM

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DOM { nodeName: 'div', attributes: { key: 'value' }, children: [ 'text node' ] } Element( nodeName: 'div', attributes: { getItem('key'), setItem('key', 'value') }, childNodes: [ TextNode('text node') ] ) virtual DOM

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./app.js const diff = (dom, vnode) => { const hasNewKids = dom.childNodes.length !== vnode.children.length; if (hasNewKids) { dom.appendChild( renderNode(vnode.children[vnode.children.length - 1]) ); return dom; } else { const newDom = renderNode(vnode); dom.parentNode.replaceChild(newDom, dom); return newDom; } };

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./app.js const diff = (dom, vnode) => { };

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./app.js const diff = (dom, vnode) => { // compare type };

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./app.js const diff = (dom, vnode) => { // compare type // compare attributes };

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./app.js const diff = (dom, vnode) => { // compare type // compare attributes // compare children };

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./app.js const diff = (dom, vnode) => { // compare type // compare attributes // compare children // optimise as much as you can! };

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www.youtube.com/watch?v=LY6y3HbDVmg

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REDUCE DOM DIFFING

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } setState(state) { this.state = Object.assign(this.state, state); renderComponent(this); } render (props, {list}) {...} }

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } setState(state) { this.prevState = Object.assign({}, this.state); this.state = Object.assign(this.state, state); renderComponent(this); } render (props, {list}) {...} }

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const renderComponent = (component) => { const rendered = component.render( component.props, component.state ); component.base = diff(component.base, rendered); }; ./our-vdom.js

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const renderComponent = (component) => { const {state, props} = component; component.state = component.prevState; component.props = component.prevProps; const rendered = component.render( component.props, component.state ); component.base = diff(component.base, rendered); }; ./our-vdom.js

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const renderComponent = (component) => { const {state, props} = component; component.state = component.prevState; component.props = component.prevProps; const rendered = component.render( component.props, component.state ); component.base = diff(component.base, rendered); }; ./our-vdom.js

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const renderComponent = (component) => { const {state, props} = component; component.state = component.prevState; component.props = component.prevProps; const rendered = component.render( component.props, component.state ); component.base = diff(component.base, rendered); }; ./our-vdom.js

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const renderComponent = (component) => { const {state, props} = component; component.state = component.prevState; component.props = component.prevProps; const rendered = component.render( component.props, component.state ); component.base = diff(component.base, rendered); }; ./our-vdom.js

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const renderComponent = (component) => { const {state, props} = component; component.state = component.prevState; component.props = component.prevProps; if (component.shouldComponentUpdate(props, state)) { component.props = props; component.state = state; const rendered = component.render( component.props, component.state ); component.base = diff(component.base, rendered); } }; ./our-vdom.js

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } setState(state) { this.prevState = Object.assign({}, state); this.state = Object.assign(this.state, state); renderComponent(this); } render (props, {list}) {...} }

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } setState(state) {...} render (props, {list}) {...} }

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./app.js class App { constructor () { this.state = { list: [ '"', '#', '$', ... ] }; this.timer = setInterval(_ => { this.setState({ list: [...this.state.list, getRandomItemFromArray(state.list)] }); }, 1000); } shouldComponentUpdate(nextProps, nextState) { return this.state.list.length !== nextState.list.length; } setState(state) {...} render (props, {list}) {...} }

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SAVE EVEN MORE WORK

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parcelRequire=function(e,r,n){var t="function"==typeof parcelRequire&&parcelRequire,i="function"==typeof require&&require;function u(n,o){if(!r[n]){if(!e[n]) {var f="function"==typeof parcelRequire&&parcelRequire;if(!o&&f)return f(n,!0);if(t)return t(n,!0);if(i&&"string"==typeof n)return i(n);var c=new Error("Cannot find module '"+n+"'");throw c.code="MODULE_NOT_FOUND",c}a.resolve=function(r){return e[n][1][r]||r};var l=r[n]=new u.Module(n);e[n] [0].call(l.exports,a,l,l.exports)}return r[n].exports;function a(e){return u(a.resolve(e))}}u.isParcelRequire=!0,u.Module=function(e) {this.id=e,this.bundle=u,this.exports={}},u.modules=e,u.cache=r,u.parent=t;for(var o=0;o 2 ? n - 2 : 0 ) , o = 2 ; o < n ; o + +)r[o-2]=arguments[o];return{nodeName:e,attributes:t,children:r}},a=function(e){var t=e.base,n=e.render(e.props,e.state),r=u(t,n);e.base=r},u=function e(t,n,r) {if(t){if("string"==typeof n)return t.nodeValue=n,t;if("function"==typeof n.nodeName){var o=new n.nodeName(n.attributes);return e(t,o.render(o.props,o.state)),t}t.childNodes.length!==n.children.length&&t.appendChild(f(n.children[n.children.length-1]));for(var i=0;i

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preact.min.js

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BENEFITS

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DECLARATIVE UI

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export default class App extends Component { ... render(props, { highlighted }) { return ( { highlighted ? 'Please stop!': 'Highlight me!' } ); } } codesandbox.io/s/rwjol2n3op

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codesandbox.io/s/rwjol2n3op export default class App extends Component { ... render(props, { highlighted }) { return React.createElement( 'button', { type: 'button', highlighted: highlighted, onclick: this.toggleHighlight }, highlighted ? 'Please stop!' : 'Highlight me!' ); } }

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codesandbox.io/s/rwjol2n3op export default class App extends Component { ... render(props, { highlighted }) { return React.createElement( 'button', { type: 'button', highlighted: highlighted, onclick: this.toggleHighlight }, highlighted ? 'Please stop!' : 'Highlight me!' ); } } It's "just" function calls

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SMART AND SELECTIVE
 RENDERING

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render() render() setState({...}) renderComponent(this) render() render() document.body APP SIDEBAR WIDGET MAIN SLIDER TABS SIDEBAR WIDGET SLIDER TABS

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LIMITED DOM OPERATIONS

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./app.js const diff = (dom, vnode) => { // compare type // compare attributes // compare children }

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function enqueueRender(component) { // ... }

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BUT IS THE vDOM THE
 SILVER BULLET?

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github.com/Polymer/lit-html github.com/WebReflection/hyperHTML

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import { html, render } from 'lit-html'; const data = { list: ['"', ..., '+'] };

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import { html, render } from 'lit-html'; const data = { list: ['"', ..., '+'] }; const App = ({list}) => { return html`

! Frontend Con 2018! !

    ${ list.map(item => html`
  • ${ item }
    • `) }
` };

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import { html, render } from 'lit-html'; const data = { list: ['"', ..., '+'] }; const App = ({list}) => { return html`

! Frontend Con 2018! !

    ${ list.map(item => html`
  • ${ item }
    • `) }
` }; render(App(data), document.body);

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html`
  • ${ item }
    • `

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    html`
  • ${ '"' }
    • ` function html(...args) { console.log(args); } [['
  • ', '
    • '], '"']

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    html`
  • ${ '"' }
    • ` function html(...args) { console.log(args); } [['
  • ', '
    • '], '"']

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    html`
  • ${ '"' }
    • ` function html(...args) { console.log(args); } [['
  • ', '
    • '], '"']

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    html`
  • ${ '"' }
    • ` function html(...args) { console.log(args); } [['
  • ', '
    • '], '"']

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    html`
  • ${ '"' } ${ Math.random() }
    • ` function html(...args) { console.log(args); } [['
  • ', ' ', '
    • ' ], '"', 0.62...]

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    html`
  • ${ '"' } ${ Math.random() }
    • ` function html(chunks, ...interpolations) { // diff only things that can change } [['
  • ', ' ', '
    • ' ], '"', 0.62...]

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    html`
  • ${ '"' } ${ Math.random() }
    • ` function html(chunks, ...interpolations) { // diff only things that can change } [['
  • ', ' ', '
    • ' ], '"', 0.62...]

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    html`
  • ${ '"' } ${ Math.random() }
    • ` function html(chunks, ...interpolations) { // diff only things that can change } [['
  • ', ' ', '
    • ' ], '"', 0.62...]

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    Only certain nodes can change!

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    A DIFFERENT APPROACH

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    NEW POSSIBILITIES

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    codepen.io/WebReflection/pen/JObreJ?editors=0010

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    I READ A LOT OF PREACT CODE

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    YOU'LL NEVER GET IT!

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    SLEEPLESS NIGHTS

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    A LOT OF BREAKS

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    AND THEN
 IT MADE SENSE

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    THERE IS NO MAGIC IN CODE!

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    THANKS FOR LISTENING SLIDES: ctfl.io/what-the-vdom
 @stefanjudis