BEM. What you can borrow from Yandex frontend dev
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This document discusses the benefits of using a Block Element Modifier (BEM) methodology for organizing CSS and HTML code into independent and reusable blocks. It provides examples of how to structure files and code for blocks, elements, modifiers, and different pages and browsers to maintain a clear separation of concerns. Developing in this way aims to make code more modular, independent, readable and maintainable.
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BEM. What you can borrow from Yandex frontend dev
- 2. BEM What you can borrow from Yandex frontend dev Frontend developer Varvara Stepanova
- 5. Over 80 services • search – web pages – images, video – goods, news, blog posts, people • web mail • web maps – traffic jams, wiki maps, taxi • hosting and sharing – files, photos, video 5
- 6. Inside Yandex • 2500 developers • 150+ frontend developers 6
- 7. Dark side of the Force
- 8. Programming is a team work
- 10. We do enjoy sharing
- 11. Web Interface
- 13. Behind the page HTML <!DOCTYPE html> <html> <head>...</head> <body> ... </body> CSS body { font: 0.8em Arial, sans-serif; margin: 0; color: black; } .sidebar ul li { 13
- 17. Block
- 20. Menu block HTML <ul class="menu"> <li><a href="/new">New titiles</a></li> <li><a href="/soon">Coming soon</a></li> <li><a href="/best">Bestsellers</a></li> ... CSS .menu { list-style: none; 20
- 21. Search block HTML <div class="search"> <input type="text" name="search" value="..."/> <input type="button" name="sbmt" value="Search"/> </div> CSS .search { padding: 2em 0; 20 21
- 22. Tabbed pane block HTML <div class="tabbed-pane"> <ul> <li>Bestsellers</li><li>...</li> </ul> <div> The Casual Vacancy, J.K. Rowling </div> </div> CSS .tabbed-pane { margin: 0.5em; ... } 22
- 23. INDEPENDENT
- 24. The page of blocks index.html <!DOCTYPE html> <html> <head>..</head> <body> <div class="head"> <div class="logo">...</div> <ul class="menu">...</ul> <div class="search">...</div> </div> <div class="layout">...</div> <div class="foot">...</div> </body> </html> 24
- 25. Repeating
- 27. Menu block HTML HTML <ul id="menu"> <ul class="menu"> ... ... CSS CSS #menu { .menu { ... ... 27
- 28. Block is independent, if • a block has its "name" – no "id" but "classname" selectors • avoids cascade • no "tag" selectors 28
- 29. Movement within a Page
- 31. Block is independent, if • a block has its "name" – no "id" but "classname" selectors • avoid cascade • no "tag" selectors 31
- 32. almost NO CASCADE when using Cascading Style Sheets 32
- 36. Moving within a Site
- 40. Pages are sets of blocks index page search page contacts page 40
- 41. CSS for different pages common.css index.css style.css contacts.css body { ... } body { { } .advert... ... } body .phone { .head { .. } ... .head { ... } .head ul li { ... .layout .books} { } a:link, ... { ... } ... .head ul li { .advert { ... } } .phone a { ... .layout .books { ... } ... } body .phone { ... } } .phone a { ... } a:link, ... { #map { ... } #map { } } 41
- 44. Pages are sets of blocks index page search page contacts page 44
- 45. CSS for every block blocks/ header.css menu.css button.css tabbed-pane.css logo.css footer.css 45
- 46. CSS for a page index.css @import url(blocks/header.css); @import url(blocks/menu.css); @import url(blocks/tabbed-pane.css); @import url(blocks/text.css); @import url(blocks/logo.css); @import url(blocks/footer.css); ... 46
- 47. Project file system blocks/ pages/ advert.css index.html books-list.css index.css head.css foot.css contacts.html logo.css contacts.css menu.css search.css book.html tabbed-pane.css book.css 47
- 48. WE NEED TO GO DEEPER
- 49. Inside a Block
- 50. Menu block HTML <ul class="menu"> <li><a href="/new">New titles</a></li> <li><a href="/soon">Coming soon</a></li> <li><a href="/best">Bestsellers</a></li> ... </ul> 50
- 51. Menu block blocks/menu.css .menu li { list-style: none; display: inline-block; padding: 0 0.5em; } 51
- 52. Menu and Dropdown blocks blocks/menu.css pages/index.html .menu li <li> { <a href="#">Bestsellers</a> list-style: none; <div class="dropdown"> display: inline-block; padding: 0 0.5em; <ul> } <li>Item One</li> <li>Item Two</li> <li>The best item</li> <li>Item Three</li> 52
- 53. Block is independent, if • a block has its "name" – no "id" but "classname" selectors • avoid cascade • no "tag" selectors 53
- 54. The style system matches rules by starting with the key selector, then moving to the left (looking for any ancestors in the rule’s selector). David Hyatt, MDN mzl.la/UuwZql 54
- 55. .menu li { 55
- 56. .menu li { 56
- 57. Menu block 57
- 58. Element
- 59. Elements 59
- 60. Search block 60
- 62. Menu page.html <ul class="menu"> <li class="menu__item"><a href="/">Index</a></li> <li class="menu__item"><a href="/new">New</a></li> <li class="menu__item"><a href="/offer">Special offer</a></li> <li class="menu__item"><a href="/shipping">Shipping</a></li> </ul> 62
- 63. Menu blocks/menu.css .menu li .tabbed-pane__tab { list-style: none; display: inline-block; .block-element padding: 0 0.5em; .block--element } .block___element 63
- 65. Files for elements blocks/ search.css menu.css search__checkbox.css menu__item.css search__autocomlete.css tabbed-pane.css book.css tabbed-pane__tab.css book__title.css tabbed-pane__pane.css book__image.css 65
- 66. Modifier
- 68. Modifier HTML <div class="tabbed-pane tabbed-pane_theme_blue"> <ul> <li class="tabbed-pane__tab">Tab 1</li> <li class="tabbed-pane__tab">Tab 2</li> </ul> <div class="tabbed-pane__pane"> ... </div> </div> 68
- 69. Modifier HTML <div class="tabbed-pane tabbed-pane_theme_blue tabbed-pane_direction_bottom"> ... </div> <input class="button button_theme_black button_size_l" ... /> 69
- 70. block-name_mod-name_mod-val tabbed-pane_theme_blue tabbed-pane_theme_white tabbed-pane_size_s tabbed-pane_size_l button_size_s button_size_l 70
- 71. Block files structure blocks/ tabbed-pane.css tabbed-pane__tab.css tabbed-pane__pane.css tabbed-pane_theme_blue.css tabbed-pane_theme_black.css tabbed-pane_direction_bottom.css 71
- 72. Taken when necessary CSS @import url(blocks/header.css); @import url(blocks/search.css); @import url(blocks/tabbed-pane.css); @import url(blocks/tabbed-pane__tab.css); @import url(blocks/tabbed-pane__pane.css); @import url(blocks/tabbed-pane_theme_blue.css); @import url(blocks/button.css); @import url(blocks/logo.css); @import url(blocks/footer.css); 72
- 74. Taken when necessary CSS <div class="tabbed-pane"> <span class=" tabbed-pane__tab tabbed-pane__tab_state_current">...</span> </div> 74
- 75. Block modifier DO affects elements 75
- 76. Cascade is possible CSS .tabbed-pane_theme_blue .tabbed-pane__tab { background-color: #9CF; } 76
- 78. File structure. The flat case blocks/ tabbed-pane.css logo.css tabbed-pane__tab.css tabbed-pane__pane.css search.css tabbed-pane_theme_blue.css search__checkbox.css tabbed-pane_theme_black.css search__autocomplete.css tabbed-pane_size_l.css tabbed-pane_size_s.css menu.css menu__item.css menu_size_l.css menu_size_s.css 78
- 79. File structure. Block folder blocks/ tabbed-pane/ menu/ tabbed-pane.css menu.css tabbed-pane__tab.css menu__item.css tabbed-pane__pane.css menu_size_l.css tabbed-pane_theme_blue.css menu_size_s.css tabbed-pane_theme_black.css tabbed-pane_size_l.css tabbed-pane_size_s.css search/ search.css logo/ search__checkbox.css logo.css search__autocomplete.css 79
- 80. File structure. Yandex way blocks/ tabbed-pane/ __tab/ _state/ tabbed-pane__tab_state_current.css tabbed-pane__tab.css __pane/ tabbed-pane__pane.css _theme/ tabbed-pane_theme_blue.css tabbed-pane_theme_black.css tabbed-pane.css 80
- 81. BEM entities • Block – combined in different ways – included one into another – independent • Element • Modifier 81
- 83. BEM is • Methodology is a way of thinking when developing • Tools do monkey job for you • Block libraries make you develop faster and better 83
- 84. IE
- 85. Render to IE the things that are IE's HTML <html> <head> <!--[if gt IE 7]><!--> <link rel="stylesheet" href="index.css"> <!--<![endif]--> <!--[if lt IE 8]> <link rel=stylesheet href="index.ie.css"> <![endif]--> </head> ... 85
- 86. Render to IE the things that are IE's HTML <html> <head> <!--[if gt IE 7]><!--> <link rel="stylesheet" href="index.css"> <!--<![endif]--> <!--[if lt IE 8]> <link rel=stylesheet href="index.ie.css"> <![endif]--> </head> ... 86
- 87. CSS file for IE CSS @import url(index.css); @import url(blocks/menu/menu.ie.css); @import url(blocks/button/button.ie.css); @import url(blocks/footer/footer.ie.css); 87
- 88. CSS file for IE CSS @import url(index.css); @import url(blocks/menu/menu.ie.css); @import url(blocks/button/button.ie.css); @import url(blocks/footer/footer.ie.css); 88
- 89. Block files for IE blocks/ tabbed-pane/ tabbed-pane.css tabbed-pane.ie.css ... menu/ menu.css menu.ie.css 89
- 90. Element files for IE blocks/ tabbed-pane/ tabbed-pane.css tabbed-pane.ie.css tabbed-pane__item.css tabbed-pane__item.ie.css tabbed-pane_theme_blue.css tabbed-pane_theme_blue.ie.css 90
- 91. Block encapsulates all index.css blocks/ menu/ @import... menu__item.css @import... menu__item.ie.css @import... menu.css @import... menu.ie.css @import... @import... index.ie.css @import... @import... @import... @import... @import... @import... 91
- 92. JavaScript
- 97. Page with JavaScript index.html <!DOCTYPE html> <html> <head> <link rel=stylesheet href="index.css"> <script type="text/javascript" src="all.js"/> </head> ... 97
- 98. Page with JavaScript index.html <!DOCTYPE html> <html> <head> <link rel=stylesheet href="index.css"> <script type="text/javascript" src="index.js"/> </head> ... 98
- 99. Pages are sets of blocks index page search page contacts page 99
- 100. JavaScript for blocks blocks/ menu/ menu.css menu.js dropdown/ dropdown.css dropdown.js tabbed-pane/ tabbed-pane.css tabbed-pane.js 100
- 101. Page JavaScript of blocks index.js borschik:include:blocks/menu/menu.js borschik:include:blocks/tabbed-pane/tabbed-pane.js ... index.js /* Menu block begins */ (function($){ $('.menu__item').on('click', function(e) { $(this).toggleClass('menu__item_state_current'); }); })(jQuery) 101
- 102. Borschik — CSS&JS flattening git.io/borschik 102
- 103. CSS flatenning index.css @import url(blocks/header.css); @import url(blocks/menu.css); ... _index.css .header { ... } .menu { ... } 103
- 104. Relative paths in CSS pages/index.css blocks/menu/menu.css @import url(blocks/menu/menu.css); .menu { background: url(menu__bg.png); } pages/_index.css .menu { background: url(../blocks/menu/menu__bg.png); } 104
- 105. general CSS HTML @import url(blocks/head/head.css); <!DOCTYPE html> @import url(blocks/search/search.css); <html> @import url(blocks/layout/layout.css); <head> @import url(blocks/menu/menu.css); <title>Awesome online bookshop</title> url(blocks/text/text.css); @import <link rel="stylesheet" href="style.css"/> @import url(blocks/foot/foot.css); <script type="text/javascript" src="magic.js"></script> </head> <body> CSS for IE <div class="head"> <ul class="menu"> @import url(index.css); <li class="menu__item"><a href="/">Home</a></li> @import url(blocks/menu/menu.ie.css); <li class="menu__item"><a href="/news">News</a></li> url(blocks/text/text.ie.css); @import ... @import url(blocks/foot/foot.ie.css); </ul> JavaScript <div class="phone">+3 71 1234567</div> </div> (function($){ <div class="layout"> ... $('.menu__item').on('click', function() { </div> </body> $(this).toggleClass('menu__item_state_current'); </html> }); })(jQuery) 105
- 106. Building Page Files
- 108. Page declaration index.xml <b:page> <b:head> <b:logo/> <b:search> <e:input/> <e:button/> </b-search> <b:menu> <e:item>Home</e:item> <e:item>Contacts</e:item> ... 108
- 109. Page declaration. BEM tree index.bemjson { block: 'page', content: [ { block: head, content: [ { block: 'logo' }, { block: 'search', .... 109
- 110. Change BEM tree if you need changes } page.html page.css page.js 110
- 111. BEM tools build pages with blocks git.io/bem-tools 111
- 112. BEM tools support many technologies blocks/ pages/ menu/ index.html menu.sass index.sass -> index.css menu.less index.coffee -> index.js menu.coffee tabbed-pane/ tabbed-pane.sass tabbed-pane.coffee 112
- 113. BEM tools support any file structure blocks/ blocks/ menu.css menu/ menu_theme_black.css __item/ menu_theme_blue.css menu__item.css menu_size_l.css _theme/ menu_size_s.css menu_theme_black.css menu-item.css menu_theme_blue.css menu-item_state_current.css _size/ menu_size_l.css tabbed-pane.css menu_size_s.css tabbed-pane_theme_black.css menu.css tabbed-pane_theme_blue.css tabbedpane-item.css tabbed-pane/ tabbedpane-pane.css logo/ logo.css 113
- 114. Multilingual
- 115. BEM tools support custom technologies blocks/ menu/ tabbed-pane.css tabbed-pane.js tabbed-pane.md 115
- 116. BEM tools support custom technologies blocks/ menu/ tabbed-pane.css tabbed-pane.js tabbed-pane.md tabbed-pane.xsl 116
- 117. Gruelling race... every day
- 118. BEMHTML template engine blocks/ menu/ tabbed-pane.css tabbed-pane.js tabbed-pane.md tabbed-pane.bemhtml 118
- 119. BEMHTML reference [RU] bit.ly/bemhtml-doc-raw 119
- 120. Libraries
- 121. Block libraries 121
- 122. BEM block library bit.ly/bem-bl-site 122
- 123. Block page and block examples 123
- 124. Block code on GitHub 124
- 125. Libraries with BEM stack git.io/bootstrap-bl git.io/jqueryui-bl git.io/modernizr-bl 125
- 126. Wanna try?
- 127. BEM-based project git.io/bem-project-stub 127
- 128. Dev Tools
- 129. Borschik — CSS & JS flattening git.io/borschik 129
- 130. CSS Optimizer BEFORE AFTER .test1 { .test1, .test2 { border: none; border: none background-color: red; } bem.info/tools/csso } .test1, .test3 { .test2 { background-color: #F00; border: none } } .test3 { background-color: #FF000; } 130
- 131. SVG Optimizer git.io/svgo 131
- 132. http://bem.info 132
- 133. Varvara Stepanova Vladimir Varankin Frontend developers toivonen@yandex-team.ru varankinv@yandex-team.ru @toivonens @tvii @bem_tw Thank you