×
Copy
Open
Link
Embed
Share
Beginning
This slide
Copy link URL
Copy link URL
Copy iframe embed code
Copy iframe embed code
Copy javascript embed code
Copy javascript embed code
Share
Tweet
Share
Tweet
Slide 1
Slide 1 text
B__E_M
Slide 2
Slide 2 text
Hi, there! I’m Luciano Battagliero @battaglr
Slide 3
Slide 3 text
Block, Element, Modifier
Slide 4
Slide 4 text
Yandex
Slide 5
Slide 5 text
~2009
Slide 6
Slide 6 text
A little bit of context OOCSS ~2010 SMACSS ~2011
Slide 7
Slide 7 text
What is it?
Slide 8
Slide 8 text
It’s a methodology
Slide 9
Slide 9 text
Heavily complemented by a set of tools, libraries and a complete technology stack
Slide 10
Slide 10 text
At its core BEM is an unified semantic for different implementations
Slide 11
Slide 11 text
That being said, this talk will be focused mainly on CSS
Slide 12
Slide 12 text
What does BEM solve?
Slide 13
Slide 13 text
Chaos /ˈkāˌäs/ noun 1. Complete disorder and confusion
Slide 14
Slide 14 text
There are two types of problems we face in CSS
Slide 15
Slide 15 text
Layout or cosmetic problems
Slide 16
Slide 16 text
Architectural problems
Slide 17
Slide 17 text
BEM attempts to help solving architecture related problems
Slide 18
Slide 18 text
Entity
Slide 19
Slide 19 text
A generic term to refer to blocks, elements or modifiers
Slide 20
Slide 20 text
Block
Slide 21
Slide 21 text
An independent and self-sufficient component of an interface
Slide 22
Slide 22 text
Provides structure, behaviour and appearance encapsulation
Slide 23
Slide 23 text
… HTML
Slide 24
Slide 24 text
… HTML
Slide 25
Slide 25 text
.modal { … } CSS
Slide 26
Slide 26 text
Blocks must be context independent, thus they should not have direct influence over other blocks
Slide 27
Slide 27 text
… HTML
Slide 28
Slide 28 text
… HTML
Slide 29
Slide 29 text
/* Don’t do this */ .modal .btn { … } CSS
Slide 30
Slide 30 text
/* Do this */ .modal__btn { … } CSS
Slide 31
Slide 31 text
Blocks can contain other blocks
Slide 32
Slide 32 text
… HTML
Slide 33
Slide 33 text
… HTML
Slide 34
Slide 34 text
Multiple instances of a block could be used across the interface
Slide 35
Slide 35 text
… … … HTML
Slide 36
Slide 36 text
… … … HTML
Slide 37
Slide 37 text
… … … HTML
Slide 38
Slide 38 text
Element
Slide 39
Slide 39 text
An internal part of a block that can not be used outside of it
Slide 40
Slide 40 text
Elements can contain other elements or blocks
Slide 41
Slide 41 text
…
HTML
Slide 42
Slide 42 text
…
HTML
Slide 43
Slide 43 text
…
HTML
Slide 44
Slide 44 text
Elements should not attempt to be a representation of the DOM structure
Slide 45
Slide 45 text
…
HTML
Slide 46
Slide 46 text
…
HTML
Slide 47
Slide 47 text
…
HTML
Slide 48
Slide 48 text
A block may not contain any element
Slide 49
Slide 49 text
Modifier
Slide 50
Slide 50 text
A variation on the appearance or behavior of a block or an element
Slide 51
Slide 51 text
…
HTML
Slide 52
Slide 52 text
…
HTML
Slide 53
Slide 53 text
…
HTML
Slide 54
Slide 54 text
…
HTML
Slide 55
Slide 55 text
…
HTML
Slide 56
Slide 56 text
…
HTML
Slide 57
Slide 57 text
Multiple modifiers can be used simultaneously on the same block or element
Slide 58
Slide 58 text
…
HTML
Slide 59
Slide 59 text
…
HTML
Slide 60
Slide 60 text
…
HTML
Slide 61
Slide 61 text
Naming conventions
Slide 62
Slide 62 text
The main purpose of a class name is to be used as a hook for adding style or behaviour
Slide 63
Slide 63 text
A class name should communicate information which helps to understand its purpose
Slide 64
Slide 64 text
Remember that a class name can not be “unsemantic”[*]
Slide 65
Slide 65 text
The “official” syntax
Slide 66
Slide 66 text
/* Basic syntax */ .block__element_modifier CSS
Slide 67
Slide 67 text
/* Basic syntax */ .block__element_modifier CSS
Slide 68
Slide 68 text
/* Basic syntax */ .block__element_modifier CSS
Slide 69
Slide 69 text
/* Basic syntax */ .block__element_modifier CSS
Slide 70
Slide 70 text
/* Key-value modifier */ .block-or-element_modifier_value CSS
Slide 71
Slide 71 text
/* Key-value modifier */ .block-or-element_modifier_value CSS
Slide 72
Slide 72 text
/* Entities with compound names */ .block-name__element-name_modifier-name CSS
Slide 73
Slide 73 text
/* Entities with compound names */ .block-name__element-name_modifier-name CSS
Slide 74
Slide 74 text
/** * All possible combinations */ .block .block_modifier .block__element .block__element_modifier CSS
Slide 75
Slide 75 text
/** * Don’t do any of these */ .element .block_modifier__element .block__element__element CSS
Slide 76
Slide 76 text
The “popular” syntax
Slide 77
Slide 77 text
/* Basic syntax */ .block__element--modifier CSS
Slide 78
Slide 78 text
/* Basic syntax */ .block__element--modifier CSS
Slide 79
Slide 79 text
/* Basic syntax */ .block__element--modifier CSS
Slide 80
Slide 80 text
/* Basic syntax */ .block__element--modifier CSS
Slide 81
Slide 81 text
/* Entities with compound names */ .block-name__element-name--modifier-name CSS
Slide 82
Slide 82 text
/* Entities with compound names */ .block-name__element-name--modifier-name CSS
Slide 83
Slide 83 text
/** * All possible combinations */ .block .block--modifier .block__element .block__element--modifier CSS
Slide 84
Slide 84 text
/** * Don’t do any of these */ .element .block--modifier__element .block__element__element CSS
Slide 85
Slide 85 text
The “CamelCase” syntax
Slide 86
Slide 86 text
/* Basic syntax */ .Block-element--modifier CSS
Slide 87
Slide 87 text
/* Basic syntax */ .Block-element--modifier CSS
Slide 88
Slide 88 text
/* Basic syntax */ .Block-element--modifier CSS
Slide 89
Slide 89 text
/* Basic syntax */ .Block-element--modifier CSS
Slide 90
Slide 90 text
/* Entities with compound names */ .BlockName-elementName--modifierName CSS
Slide 91
Slide 91 text
/* Entities with compound names */ .BlockName-elementName--modifierName CSS
Slide 92
Slide 92 text
/** * All possible combinations */ .Block .Block--modifier .Block-element .Block-element--modifier CSS
Slide 93
Slide 93 text
/** * Don’t do any of these */ .element .Block--modifier-element .Block-element-element CSS
Slide 94
Slide 94 text
Syntax comparison
Slide 95
Slide 95 text
/* “Official” */ block-name__element-name_modifier-name /* “Popular” */ block-name__element-name--modifier-name /* “CamelCase” */ BlockName-elementName--modifierName CSS
Slide 96
Slide 96 text
/* “Official” */ block-name__element-name_modifier-name /* “Popular” */ block-name__element-name--modifier-name /* “CamelCase” */ BlockName-elementName--modifierName CSS
Slide 97
Slide 97 text
/* “Official” */ block-name__element-name_modifier-name /* “Popular” */ block-name__element-name--modifier-name /* “CamelCase” */ BlockName-elementName--modifierName CSS
Slide 98
Slide 98 text
/* “Official” */ block-name__element-name_modifier-name /* “Popular” */ block-name__element-name--modifier-name /* “CamelCase” */ BlockName-elementName--modifierName CSS
Slide 99
Slide 99 text
It has been scientifically proven that BEM class names are ugly
Slide 100
Slide 100 text
Mix
Slide 101
Slide 101 text
A combination of different entities on a single DOM node
Slide 102
Slide 102 text
HTML
Slide 103
Slide 103 text
HTML
Slide 104
Slide 104 text
Implementation guidelines
Slide 105
Slide 105 text
Only define entities using class selectors
Slide 106
Slide 106 text
.icon { … } CSS
Slide 107
Slide 107 text
Use descendant selectors only when needed
Slide 108
Slide 108 text
/* Don’t do this */ .menu .menu__item { … } CSS
Slide 109
Slide 109 text
/* Do this */ .menu--horizontal .menu__item { … } CSS
Slide 110
Slide 110 text
Do not use type or id selectors
Slide 111
Slide 111 text
/* Don’t do this */ button { … } CSS
Slide 112
Slide 112 text
/* Do this */ .button { … } CSS
Slide 113
Slide 113 text
/* Don’t do this */ #breadcrumb { … } CSS
Slide 114
Slide 114 text
/* Do this */ .breadcrumb { … } CSS
Slide 115
Slide 115 text
Do not declare styles outside of blocks
Slide 116
Slide 116 text
/* Don’t do this */ ul { list-style: none; } CSS
Slide 117
Slide 117 text
/* Do this */ .menu { list-style: none; } CSS
Slide 118
Slide 118 text
This usually means no global styles and no global “resets”
Slide 119
Slide 119 text
That’s just a part of it!
Slide 120
Slide 120 text
There’s a lot more about BEM. Go to bem.info and find out!
Slide 121
Slide 121 text
Questions?
Slide 122
Slide 122 text
Thanks!