When Virtual DOM Diffing Is a Little Too Clever

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⚡ When Virtual DOM Diffing Is a Little Too Clever by Diana MacDonald

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- Designer - Team Lead - Design Systems - Author - Coder Diana MacDonald @DiDoesDigital

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- Designer - Team Lead - Design Systems - Author - Coder Diana MacDonald @DiDoesDigital

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Today - Virtual DOM diffing - Screen readers - ARIA live regions - aria-atomic - Double announcer regions - Web Speech API

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Virtual DOM

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Virtual DOM

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Change Detection

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Incremental DOM

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Actual DOM: Elements

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Actual DOM: Console

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Virtual DOM div p div #text #comment

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img #text Virtual DOM: diffing

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Virtual DOM: ﬁnal state img div p div #comment

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Screen readers

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ARIA live regions

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{message}

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{message}

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{message}

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Announcing dynamic changes

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{this.state.message}

{this.state.value} Rendering ARIA live (this could work) #

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Rendering ARIA live (this won't work!) {newMessage ?

{this.state.message}

: null} $

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aria-atomic="true"

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{message}

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{message}

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The estimated time of arrival is 2.30pm.

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The estimated time of arrival is 2.40pm.

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The estimated time of arrival is 2.40pm. There's been a delay.

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The estimated time of arrival is 2.40pm. There's been a delay.

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Virtual DOM + aria-atomic

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The estimated time of arrival is {time}. {delayMessage}

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The estimated time of arrival is {time}. {delayMessage}

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The estimated time of arrival is 2.40pm. There's been a delay.

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Double announcers

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{message1}

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{message1}

{message2}

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The estimated time of arrival is 2.30pm.

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The estimated time of arrival is 2.40pm. There's been a delay.

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Cancelled. Find alternative transport.

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https://github.com/dequelabs/ngA11y https://github.com/AlmeroSteyn/react-aria-live https://github.com/Jinjiang/vue-a11y-utils Double announcer packages

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Test

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DIVs for everything

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Semantic markup #

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CSS animations (written without React) .my-node-enter { opacity: 1; transition: opacity 200ms; } .my-node-exit { opacity: 0; transition: opacity 200ms; } $

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.my-node-enter { opacity: 0; } .my-node-enter-active { opacity: 1; transition: opacity 200ms; } .my-node-exit { opacity: 1; } .my-node-exit-active { opacity: 0; transition: opacity 200ms; } CSS animations (written for React) #

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{message}

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{showNotification ? {message} : null } $

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Web Speech API: speech synthesis

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let synth = window.speechSynthesis; if (window.SpeechSynthesisUtterance) { let utterThis = new SpeechSynthesisUtterance("notevole"); synth.speak(utterThis); }

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let synth = window.speechSynthesis; if (window.SpeechSynthesisUtterance) { let utterThis = new SpeechSynthesisUtterance("notevole"); synth.speak(utterThis); }

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Constraints and creativity

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Questions? Diana MacDonald | @DiDoesDigital HK Grotesk™ is an open source sans serif typeface by Hanken Design Co.  Iosevka is an open source monospace typeface by Belleve Invis See DiDoesDigital.com for the slides and the book