Slide 1

Slide 1 text

Modular CSS with @okonetchnikov

Slide 2

Slide 2 text

Andrey Okonetchnikov @okonetchnikov

Slide 3

Slide 3 text

No content

Slide 4

Slide 4 text

ColorSnapper http://colorsnapper.com

Slide 5

Slide 5 text

kaffemik Zollergasse 5, 1070 Wien

Slide 6

Slide 6 text

I ❤ Open Source github.com/okonet/react-dropzone github.com/okonet/lint-staged and many more…

Slide 7

Slide 7 text

I design & develop User Interfaces

Slide 8

Slide 8 text

Building scalable User Interfaces

Slide 9

Slide 9 text

No content

Slide 10

Slide 10 text

No content

Slide 11

Slide 11 text

No content

Slide 12

Slide 12 text

No content

Slide 13

Slide 13 text

– http://www.csszengarden.com/ “CSS allows complete and total control over the style of a hypertext document…”

Slide 14

Slide 14 text

CSS was designed for documents, not for web-applications

Slide 15

Slide 15 text

No content

Slide 16

Slide 16 text

No content

Slide 17

Slide 17 text

No content

Slide 18

Slide 18 text

User Interface ∋ Components

Slide 19

Slide 19 text

Libraries & Frameworks based on components

Slide 20

Slide 20 text

What are UI Components?

Slide 21

Slide 21 text

List component Button Button

Slide 22

Slide 22 text

List Item Component Button

Slide 23

Slide 23 text

Atomic components Button

Slide 24

Slide 24 text

Let’s build a component!

Slide 25

Slide 25 text

In React.js everything is a component!

Slide 26

Slide 26 text

Button component Default Active Disabled

Slide 27

Slide 27 text

Button.js 1 const Button = ({ children }) => { 2 return ( 3 6 { children } 7 8 ) 9 }

Slide 28

Slide 28 text

Button.js 1 const Button = ({ children }) => { 2 return ( 3 7 8 { children } 9 10 11 ) 12 }

Slide 29

Slide 29 text

Button.js 1 const Button = ({ children, disabled }) => { 2 return ( 3 8 9 { children } 10 11 12 ) 13 }

Slide 30

Slide 30 text

Button.js 1 const Button = ({ children, disabled }) => { 2 let classNames = 'btn' 3 if (disabled) classNames += ' disabled' 4 return ( 5 10 11 { children } 12 13 14 ) 15 }

Slide 31

Slide 31 text

Button.js 1 const Button = ({ children, disabled, active }) => { 2 let classNames = 'btn' 3 if (disabled) classNames += ' disabled' 4 if (active) classNames += ' active’ 5 return ( 6 11 12 { children } 13 14 15 ) 16 }

Slide 32

Slide 32 text

Let’s add some CSS 1 .btn { 2 /* styles for button */ 3 } 4 5 .active { 6 /* styles for active button */ 7 background-color: blue; 8 } 9 10 .label { 11 /* styles for button label */ 12 }

Slide 33

Slide 33 text

Button component Default Active Disabled Default Disabled Active

Slide 34

Slide 34 text

Button component Active Click me! Active

Slide 35

Slide 35 text

Star component

Slide 36

Slide 36 text

Star.js 1 const Star = ({ active }) => { 2 let classNames = 'star' 3 if (active) classNames += ' active' 4 return ( 5 6 ) 7 }

Slide 37

Slide 37 text

Let’s add some CSS 1 .star { 2 /* styles for star */ 3 } 4 5 .active { 6 /* styles for active star */ 7 background-color: orange; 8 } 9

Slide 38

Slide 38 text

Star component

Slide 39

Slide 39 text

f(props, state) => UI

Slide 40

Slide 40 text

UI components should be pure, modular & isolated

Slide 41

Slide 41 text

• Props • State • Styles Button

Slide 42

Slide 42 text

• Props • State • Styles Button • Props • State • Styles • Props • State • Styles

Slide 43

Slide 43 text

• Props • State • Styles Button • Props • State • Styles • Props • State • Styles

Slide 44

Slide 44 text

and yet…

Slide 45

Slide 45 text

• Props • State • Styles Button • Props • State • Styles • Props • State • Styles Global styles

Slide 46

Slide 46 text

No content

Slide 47

Slide 47 text

Global CSS 1 .btn { 2 /* styles for button */ 3 } 4 5 .active { 6 /* styles for active button */ 7 background-color: blue; 8 } 9 10 .label { 11 /* styles for button label */ 12 } 1 .star { 2 /* styles for star */ 3 } 4 5 .active { 6 /* styles for active star */ 7 background-color: orange; 8 } 9

Slide 48

Slide 48 text

.btn.active

Slide 49

Slide 49 text

.content .albums .album .btn

Slide 50

Slide 50 text

No content

Slide 51

Slide 51 text

http://www.standardista.com/css3/css-specificity/

Slide 52

Slide 52 text

Debugging CSS

Slide 53

Slide 53 text

.btn.active

Slide 54

Slide 54 text

Where are my styles?

Slide 55

Slide 55 text

Where is my CSS? 1 const Button = ({ children }) => { 2 return ( 3 7 8 { children } 9 10 11 ) 12 }

Slide 56

Slide 56 text

Where is my CSS? Where is this class coming from? 1 const Button = ({ children }) => { 2 return ( 3 7 8 { children } 9 10 11 ) 12 }

Slide 57

Slide 57 text

Let’s search quickly…

Slide 58

Slide 58 text

CSS Monolith!

Slide 59

Slide 59 text

Refactoring application.css

Slide 60

Slide 60 text

Problems with CSS in Web Applications Disconnected from component’s code Implicit dependencies No styles isolation No composition & code sharing

Slide 61

Slide 61 text

1. Split your code

Slide 62

Slide 62 text

Components > Files public ├── images │ └── icon.svg ├── javascripts │ ├── Button.js │ └── Dropdown.js └── stylesheets ├── Buttons.css └── Dropdown.css public ├── images │ └── icon.svg ├── javascripts │ └── application.js └── stylesheets └── application.css

Slide 63

Slide 63 text

1. Split & co-locate

Slide 64

Slide 64 text

Separation of concerns? public ├── images │ └── icon.svg ├── javascripts │ ├── Button.js │ └── Dropdown.js └── stylesheets ├── Buttons.css └── Dropdown.css

Slide 65

Slide 65 text

Separation of concerns technologies public ├── images │ └── icon.svg ├── javascripts │ ├── Button.js │ └── Dropdown.js └── stylesheets ├── Buttons.css └── Dropdown.css

Slide 66

Slide 66 text

Separation of concerns components ├── Button │ ├── Button.css │ ├── Button.js │ ├── Button.spec.js │ ├── icon.svg │ └── index.js └── Dropdown public ├── images │ └── icon.svg ├── javascripts │ ├── Button.js │ └── Dropdown.js └── stylesheets ├── Buttons.css └── Dropdown.css

Slide 67

Slide 67 text

2. Dependencies

Slide 68

Slide 68 text

CSS pre-processors?

Slide 69

Slide 69 text

Dependencies in Sass 1 /* Global styles */ 2 @import 'reset.css'; 3 @import 'typography.css'; 4 @import 'grid.css'; 5 6 /* Components */ 7 @import 'button.css';

Slide 70

Slide 70 text

Where is my CSS? Where is this class coming from? 1 const Button = ({ children }) => { 2 return ( 3 7 8 { children } 9 10 11 ) 12 }

Slide 71

Slide 71 text

No content

Slide 72

Slide 72 text

Explicit dependencies FTW! 1 import './Button.css' 2 3 const Button = ({ children, disabled, active }) => { 4 let classNames = 'btn' 5 if (disabled) classNames += ' disabled' 6 if (active) classNames += ' active' 7 return ( 8 13 14 { children } 15 16 17 ) 18 } 19 export default Button

Slide 73

Slide 73 text

No content

Slide 74

Slide 74 text

1. We can’t require CSS in JS

Slide 75

Slide 75 text

2. Browsers expect and

Slide 76

Slide 76 text

3. We want minimal number of HTTP requests

Slide 77

Slide 77 text

Common build tools operate on file trees

Slide 78

Slide 78 text

Dependency graph

Slide 79

Slide 79 text

http://webpack.github.io/

Slide 80

Slide 80 text

Allow requiring CSS with Webpack 1 module.exports = { 2 module: { 3 loaders: [ 4 { 5 test: /\.css$/, 6 use: ["style-loader", "css-loader"] 7 } 8 ] 9 } 10 };

Slide 81

Slide 81 text

Now we can import CSS in JS! 1 import './Button.css' 2 3 const Button = ({ children, disabled, active }) => { 4 let classNames = 'btn' 5 if (disabled) classNames += ' disabled' 6 if (active) classNames += ' active' 7 return ( 8 13 14 { children } 15 16 17 ) 18 } 19 export default Button

Slide 82

Slide 82 text

No content

Slide 83

Slide 83 text

Tips & Tricks ✅ Split your code by components ✅ One directory per UI component ✅ One CSS file per UI component ✅ Explicit dependencies ✅ Co-locate JS, CSS and assets

Slide 84

Slide 84 text

How are we doing so far? No styles isolation Composition & code sharing ✅ Disconnected from component’s code ✅ Implicit dependencies

Slide 85

Slide 85 text

3. Styles isolation

Slide 86

Slide 86 text

Global CSS 1 .btn { 2 /* styles for button */ 3 } 4 5 .active { 6 /* styles for active button */ 7 background-color: blue; 8 } 9 10 .label { 11 /* styles for button label */ 12 } 1 .star { 2 /* styles for star */ 3 } 4 5 .active { 6 /* styles for active star */ 7 background-color: orange; 8 } 9

Slide 87

Slide 87 text

BEM https://en.bem.info/

Slide 88

Slide 88 text

B E M Block Element Modifier Button Button__label Button --active

Slide 89

Slide 89 text

Without BEM Click me!

Slide 90

Slide 90 text

With BEM Click me!

Slide 91

Slide 91 text

Using BEM 1 /* Button.css */ 2 3 .Button { /* general rules */ } 4 .Button --disabled { /* disabled rules */ } 5 .Button --active { /* active rules */ } 6 .Button__label { /* label rules */ }

Slide 92

Slide 92 text

Using BEM 1 import './Button.css' 2 3 const Button = ({ children, disabled, active }) => { 4 let classNames = 'Button' 5 if (disabled) classNames += ' Button --disabled' 6 if (active) classNames += ' Button --active' 7 return ( 8 13 14 { children } 15 16 17 ) 18 } 19 export default Button

Slide 93

Slide 93 text

BEM ✅ Global namespace ✅ Styles isolation Not beginner friendly Very verbose Requires discipline Long class names

Slide 94

Slide 94 text

@markdalgleish

Slide 95

Slide 95 text

CSS-modules https://github.com/css-modules/css-modules

Slide 96

Slide 96 text

No content

Slide 97

Slide 97 text

How CSS-modules work

Slide 98

Slide 98 text

Before: BEM-style 1 /* Button.css */ 2 3 .Button { /* general rules */ } 4 .Button --disabled { /* disabled rules */ } 5 .Button --active { /* active rules */ } 6 .Button__label { /* label rules */ }

Slide 99

Slide 99 text

After: CSS-modules 1 /* Button.css */ 2 3 .root { /* general rules */ } 4 .disabled { /* disabled rules */ } 5 .active { /* active rules */ } 6 .label { /* label rules */ }

Slide 100

Slide 100 text

The result 1 styles: { 2 root: "Button__root__abc5436", 3 disabled: "Button__disabled__def6 4 active: "Button__active__1638bcd" 5 label: "Button__label__5dfg462" 5 } 1 /* Button.css */ 2 3 .root { /* general rules */ } 4 .disabled { /* disabled rules */ } 5 .active { /* active rules */ } 6 .label { /* label rules */ }

Slide 101

Slide 101 text

Before: BEM-style 1 import './Button.css' 2 3 const Button = ({ children, disabled, active }) => { 4 let classNames = 'Button' 5 if (disabled) classNames += ' Button --disabled' 6 if (active) classNames += ' Button --active' 7 return ( 8 13 14 { children } 15 16 17 ) 18 } 19 export default Button

Slide 102

Slide 102 text

1 import styles from './Button.css' 2 3 const Button = ({ children, disabled, active }) => { 4 let className = {styles.root} 5 if (disabled) className = {styles.disabled} 6 if (active) className = {styles.active} 7 return ( 8 13 14 { children } 15 16 17 ) 18 } 19 export default Button After: CSS-modules

Slide 103

Slide 103 text

The result Click me! Click me!

Slide 104

Slide 104 text

1 import styles from './Button.css' 2 3 const Button = ({ children, disabled, active }) => { 4 let className = {styles.root} 5 if (disabled) className = {styles.disabled} 6 if (active) className = {styles.active} 7 return ( 8 13 14 { children } 15 16 17 ) 18 } 19 export default Button After: CSS-modules

Slide 105

Slide 105 text

Enabling CSS-modules 1 // webpack.config.js 2 3 module.exports = { 4 module: { 5 loaders: [ 6 { 7 test: /\.css$/, 8 loader: "css" 9 } 10 ] 11 } 12 };

Slide 106

Slide 106 text

Enabling CSS-modules 1 // webpack.config.js 2 3 module.exports = { 4 module: { 5 loaders: [ 6 { 7 test: /\.css$/, 8 loader: "css?modules" 9 } 10 ] 11 } 12 };

Slide 107

Slide 107 text

BEM-like class names 1 // webpack.config.js 2 3 module.exports = { 4 module: { 5 loaders: [ 6 { 7 test: /\.css$/, 8 loader: "css?modules 9 &localIdentName=[name]__[local]__[hash:base64:5]" 10 11 } 12 ] 13 } 14 };

Slide 108

Slide 108 text

import styles from './Button.css' /* styles = { button: ‘Button__root__3fslE’, label: ‘Button__label__I8bKh’ } */ name local hash BEM-like class names

Slide 109

Slide 109 text

BEM for free! ❤

Slide 110

Slide 110 text

4. Composition & code sharing

Slide 111

Slide 111 text

Composition with Sass 1 /* Button.css */ 2 3 .Button { /* common rules */ } 4 .Button --disabled { /* disabled rules */ } 5 .Button --active { /* active rules */ }

Slide 112

Slide 112 text

Composition with Sass 1 .Button --common { /* common rules */ } 2 .Button --disabled { 3 @extends .Button --common; 4 /* gray color, light background */ 5 } 6 .Button --active { 7 @extends .Button --common; 8 /* white color, blue background */ 9 }

Slide 113

Slide 113 text

Composition with Sass 1 .Button --common, .Button --disabled, .Button --active { 2 /* common rules */ 3 } 4 .Button --disabled { 5 /* gray color, light background */ 6 } 7 .Button --active { 8 /* white color, blue background */ 9 }

Slide 114

Slide 114 text

Composition with CSS-modules 1 /* Button.css */ 2 3 .root { /* general rules */ } 4 .disabled { /* disabled rules */ } 5 .active { /* active rules */ }

Slide 115

Slide 115 text

Composition with CSS-modules 1 /* Button.css */ 2 3 .root { /* general rules */ } 4 .disabled { 5 composes: root; 6 /* disabled rules */ 7 } 8 .active { 9 composes: root; 10 /* active rules */ 11 }

Slide 116

Slide 116 text

Composition with CSS-modules 1 styles: { 2 root: "Button__root__abc5436", 3 disabled: "Button__root__abc5436 Button__disabled__def6547", 4 active: "Button__root__abc5436 Button__active__1638bcd" 5 }

Slide 117

Slide 117 text

Use only one class name! 1 /* Don't do this */ 2 `class=${[styles.normal, styles['active']].join(" ")}` 3 4 /* Using a single name makes a big difference */ 5 `class=${styles['active']}` 6 7 /* camelCase makes it even better */ 8 `class=${styles.isActive}`

Slide 118

Slide 118 text

The result Click me! Click me!

Slide 119

Slide 119 text

Compose from other files! 1 /* colors.css */ 2 .active { 3 background-color: blue; 4 } 5 .secondary { 6 background-color: #999; 7 } 1 /* Button.css */ 2 .root { /* general rules */ } 3 .active { 4 composes: root; 5 composes: active from ' ../colors.css'; 6 /* active rules */ 7 }

Slide 120

Slide 120 text

Or use variables! /* variables.css */ @value small: (max-width: 599px); /* component.css */ @value small from "./variables.css"; .pageContent { background: green; @media small { background: red; } }

Slide 121

Slide 121 text

5. MinificationBonus

Slide 122

Slide 122 text

Minification 1 // webpack.config.js 2 3 module.exports = { 4 module: { 5 loaders: [ 6 { 7 test: /\.css$/, 8 loader: "css?modules" 9 } 10 ] 11 } 12 };

Slide 123

Slide 123 text

Minification Click me! Click me!

Slide 124

Slide 124 text

Solved with CSS-modules ✅ No styles isolation ✅ Constants sharing ✅ Minification ✅ Disconnected from component’s code ✅ Implicit dependencies

Slide 125

Slide 125 text

CSS-modules overview

Slide 126

Slide 126 text

Local by default but allow exceptions .local-class { color: red; } :global(.prefix-modal-open) .local-class { color: green; }

Slide 127

Slide 127 text

Composition .common { /* all the common styles you want */ } .normal { composes: common; /* anything that only applies to Normal */ } .disabled { composes: common; /* anything that only applies to Disabled */ }

Slide 128

Slide 128 text

Explicit dependencies .otherClassName { composes: className from "./style.css"; }

Slide 129

Slide 129 text

Import variables /* variables.css */ @value small: (max-width: 599px); /* component.css */ @value small from "./breakpoints.scss"; .pageContent { background: green; @media small { background: red; } }

Slide 130

Slide 130 text

Use with pre-processors like Sass or Less :global { .this-is-global { color: yellow; } .potential-collision-city { color: crap; } }

Slide 131

Slide 131 text

Works on server, too! https://github.com/css-modules/postcss-modules https://github.com/css-modules/cssm-rails

Slide 132

Slide 132 text

No content

Slide 133

Slide 133 text

FTW!

Slide 134

Slide 134 text

PostCSS http://postcss.org

Slide 135

Slide 135 text

Like Babel, but for CSS

Slide 136

Slide 136 text

How PostCSS works

Slide 137

Slide 137 text

What’s possible?

Slide 138

Slide 138 text

Autoprefixer :full-screen { } :-webkit-:full-screen { } :-moz-:full-screen { } :full-screen { }

Slide 139

Slide 139 text

Sass/less syntax

Slide 140

Slide 140 text

Browser hacks

Slide 141

Slide 141 text

Local CSS .name { color: gray; } .Logo__name__SVK0g { color: gray; }

Slide 142

Slide 142 text

CSS next :root { --red: #d33; } a { &:hover { color: color(var( --red) a(54%)); } } a:hover { color: #dd3333; color: rgba(221, 51, 51, 0.54); }

Slide 143

Slide 143 text

Stylelint a { color: #4f; }

Slide 144

Slide 144 text

PostCSS overview 1. More powerful and faster than pre-processors thanks AST 2. Lots of plugins and easy to write your own 3. Tools! stylelint or automatic properties sorting 4. IDE Support (WebStorm, Atom, Sublime) 5. Shared constants between CSS and JS 6. Works not only with SPAs or React 7. It’s just CSS*

Slide 145

Slide 145 text

http://postcss.org

Slide 146

Slide 146 text

How to setup

Slide 147

Slide 147 text

Example setup with Webpack module.exports = { module: { loaders: [ { test: /\.css$/, use: ['style-loader', 'css-lader', 'postcss-loader'] } ] }, postcss: function() { return [ require('autoprefixer')({ browsers: ['last 2 version'] }) ]; } };

Slide 148

Slide 148 text

http://postcss.parts/ by @mxstbr

Slide 149

Slide 149 text

Lint CSS as pre-commit hook 1 { 2 "lint-staged": { 3 "*.css": "stylelint" 4 }, 5 "pre-commit": "lint-staged", 6 "stylelint": { 7 "extends": "stylelint-config-standard" 8 } 9 } https://github.com/okonet/lint-staged

Slide 150

Slide 150 text

Do I need it?

Slide 151

Slide 151 text

Do I need it? ✅ You work in a team ✅ You plan to update your CSS in the future ✅ You use third-party CSS and don’t want to break things ✅ You care about code readability and reusability ✅ You hate manual work

Slide 152

Slide 152 text

What about CSS-in-JS?

Slide 153

Slide 153 text

No content

Slide 154

Slide 154 text

Worth checking out by @mxstbr and @glennmaddern by @oleg008

Slide 155

Slide 155 text

– Glen Maddern https://github.com/css-modules/css-modules/issues/187#issuecomment-257752790 “[…] I wouldn’t suggest using any CSS-in-JS tool over CSS Modules for decent-sized projects in the near term.”

Slide 156

Slide 156 text

Final thoughts

Slide 157

Slide 157 text

It’s not about writing code, it’s about reading it.

Slide 158

Slide 158 text

Build isolated components.

Slide 159

Slide 159 text

Separate concerns, not technologies.

Slide 160

Slide 160 text

Treat CSS seriously. It’s here to stay.

Slide 161

Slide 161 text

Choose the right tool for the job.

Slide 162

Slide 162 text

Stay open-minded & keep experimenting!

Slide 163

Slide 163 text

Thank you!

Slide 164

Slide 164 text

Andrey Okonetchnikov @okonetchnikov http://okonet.ru https://github.com/okonet Freelance UI-Developer