Bulletproof CSS in React

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with @DavidWells davidwells.io/talks/react-css Bulletproof CSS in React

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UI/UX Engineer at React and Redux Training for companies Next Class Saturday, July 16th in SF register.reactclass.com Tweet at me @DavidWells DavidWells.io

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No content

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ux.mulesoft.com

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Challenge Make components stand alone Make them work in legacy applications Avoid external collisions and dont collide with others Have styles & assets consumable by others

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Obligatory Peter Griﬃn CSS gif

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GLOBAL PROBLEMS

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Global CSS Namespace collisions are the greatest threat we face today - Donald Trump

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HOW DO WE SOLVE THIS?

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Localized CSS

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Raw CSS (OOCSS, SMACSS, BEM, SUIT) Inline styles in JSX CSS-in-JS PostCSS + CSS Modules Current styling landscape

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https://github.com/MicheleBertoli/css-in-js

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1. Inline Styles

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Easy to implement Recompute styles at anytime Dynamic state based styles etc import React from 'react' class ShamWOW extends React.Component { render(){ const styles = { color: (this.props.danger) ? 'red' : 'black' fontSize: '15px' } const otherStyles = { color: 'purple' fontSize: '12px' } return (

WOW!

) } }

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No Pseudo Classes/Elements No Media Queries No vender autopreﬁxing No Animations/keyframes !important for overrides No Style Fallbacks Composition? Performance (large HTML, larger JS) Debugging is hard INLINE STYLES GOTCHAS

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2. CSS in JS

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import React, {Component} from 'react' import {StyleSheet, css} from 'aphrodite' const styles = StyleSheet.create({ container: { textAlign: 'center' }, button: { backgroundColor: '#ff0000', width: '320px', borderRadius: '5px', ':hover': { color: '#fff', }, '@media (max‐width: 480px)': { width: '160px' } } }) export default class Button extends Component { render() { return (

Click me!

); } }

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Flash of Incorrectly Styled Content* Pseudo Classes/Elements* Media Queries* No Style Fallbacks Animations/keyframes* Debugging is hard* (no sourcemaps) Performance (larger bundle, DOM calcs) library/ﬂavor lock-in Globals? Composable? CSS in JS Considerations

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3. PostCSS + CSS Modules

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My Javascript fatique senses are tingling What are these?

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Local (and global) scope AST is very very powerful Huge plugin ecosystem Write normal CSS and more... Why PostCSS?

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WHAT DOES THIS LOOK LIKE?

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Component architecture /src/components/ └── Button/ # Component folder ├── Button.js # src code ├── Button.css # styles ├── Button.spec.js # tests ├── index.js # Exports your component └── examples/ # Usage Examples └── button_usage.js # Examples of component usage

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Localized Styles via PostCSS + CSS modules /* Button.js React Component */ import React from 'react' import styles from './Button.css' class Button extends React.Component { render(){ const text = this.props.text return (

{text}

) } }

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CSS as per usual /* Button.css */ .wrapper { font‐size: 20px; } .button { border: 20px solid #bada55; }

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How CSS modules work /* Button.js */ import React from 'react' /* styles is imported as an object with classnames as keys */ import styles from './Button.css' /* styles = { button: "Button__button___I_bKh" <‐‐‐ Filename__classname__HASH wrapper: "Button__wrapper___3fslE" } */ class Button extends React.Component { render(){ const text = this.props.text return (

{text}

) } }

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The end result

My button Text

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Other beneﬁts Use CSS4 Polyﬁll Flexbox back to IE8 a11y rules linting?!?!! intial: all; Composability Critical CSS paths Separate out all mediaQueries (bit.ly/responsiblejs) Perf gains dev linting via styleLint Designers can write* *gasp* ability to use Global

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IS GLOBAL CSS ALL BAD? NOPE! modal, drawer, etc. classes on body Sharing keyframe animations External selector hooks (double edged sword) Sometimes you want the cascade

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.local‐class { color: red; } :global(.prefix‐modal‐open) .local‐class { color: green; } /* or */ :global { .this‐is‐global { color: yellow; } .potential‐collision‐city { color: crap; } } You decide Local by default, global when you want

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DO I NEED THIS? Are you working on a team? Are you including third party CSS? Markup running inside of a third party environment? Do you want raw AST power? Want your styles to look correct no matter what?

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Whats the real power here? AST

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FIX CSS FOREVER WOOOOOOOOOOOOO!!!!!

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CAVEATS No react native* Requires build step (but what doesn't these days) No "dynamic" computed styles based on state* Be careful of inventing your own syntax Don't go nuts with plugins Testing quirks if asserting on localized classnames You have to write CSS*

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WHICH APPROACH WINS? ALL OF THEM!

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Our choice PostCSS + inlineStyles PostCSS handles majority of styling When computed values are needed inlineStyles on the `style`

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Javascript powered variables 16. /* require global variables */ 17. require('postcss-simple-vars')({ 18. variables: function () { 19. return require('./variables') 20. }, 21. unknown: function (node, name, result) { 22. node.warn(result, 'Unknown variable ' + name) 23. } 10. /* enable mixins like Sass/Less */ 11. require('postcss-mixins')({ 12. mixins: require('./mixins') 13. }), 14. /* enable nested css selectors like Sass/Less */ 15. require('postcss-nested'), 24. }), 25. /* PostCSS plugin for making calculations with math.js */ 26. require('postcss-math'), 27. /* transform W3C CSS color function to more compatible CSS. */ 28. require('postcss-color-function') 29. ]

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Mixin & variable usage in CSS .hero { @mixin DinProLight; /* defined in mixins.js */ color: $primaryBlue; /* defined in variables.js */ }

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Variable usage in JS import React from 'react' import variables from 'path/to/global‐variables' class Button extends React.Component { render(){ const styles = { color: variables.primary zIndex: variables.aboveModal } return (

WOW!

) } }

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Best of both worlds PostCSS (AST JS infused CSS) and CSS in JS when needed

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Tips & Tricks

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Build for production localIdentName: [hash:base64:4] module: { loaders: [ { test: /.css/, loaders: ['style‐loader', 'css‐loader?modules&localIdentName=[hash:base64:4]!postcss‐loader'], } ] }, Output:

My button Text

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BEM FO FREE localIdentName: [name]__[local] module: { loaders: [ { test: /.css/, loaders: ['style‐loader', 'css‐loader?modules&localIdentName=[name]__[local]!postcss‐loader'], } ] }, Output:

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npm i classnames via @jedWatson import styles from './Button.css' import classnames from 'classnames' ... const { className, isGhost, disabled, isLoading } = this.props const propBasedClasses = { [styles.ghost]: isGhost, /* if isGhost === true */ [styles.disabled]: disabled || isLoading } const classes = classNames( styles.button, /* localized styles */ className, /* user specified classNames */ propBasedClasses /* prop based classnames */ )

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http://postcss.parts via @mxstbr

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catch undeﬁned via @Chrisui .undefined { display: flex !important; position: fixed !important; top: 0 !important; right: 0 !important; bottom: 0 !important; left: 0 !important; background: red !important; color: white !important; justify‐content: center !important; align‐items: center !important; font‐size: 30px !important; font‐weight: bold !important; } .undefined::after { display: block !important; padding: 15px 30px !important; content: 'ERROR! You are missing a class definition in your css module! Inspect me to find out where.' !important }

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http://cssnext.io via @MoOx

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Questions? React and Redux Training Next Class Saturday, July 16th in SF React Basics through Redux and Serverside Rendering register.reactclass.com Tweet at me @DavidWells DavidWells.io

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Phenomic presentation bit.ly/phenomic-sites

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Questions? React and Redux Training Next Class Saturday, July 16th in SF React Basics through Redux and Serverside Rendering register.reactclass.com Tweet at me @DavidWells DavidWells.io