Taming CSS Selectors

TAMING SELECTORS
sanity for our stylesheets

SIZE OF THE CSS FILE AND
IMPLIED HTTP REQUESTS
are the biggest factor for CSS performance

REFLOWS AND
RENDERING TIME
are (much!) less important

DUPLICATION IS WORSE
THAN STALE RULES
because we have tools to deal with the later

DEFINE DEFAULT VALUES
Don’t repeat this code in every object

#weatherModule h3{color:red;}
#tabs h3{color:blue}


X


X

h1, .h1{...}
h2, .h2{...}
h3, .h3{...}
h4, .h4{...}
h5, .h5{...}
h6, .h6{...}

DEFINE STRUCTURE IN A
SEPARATE CLASS
block
inner
hd

bd

ft

div.error{...}

STYLE CLASSES
rather than elements

X
div.error{...}

STYLE CLASSES

.error{ most of the code goes here }

X
div.error{...}

STYLE CLASSES

.error{ most of the code goes here }
div.error{ }
p.error{ exceptions only }
em.error{ }

div{...}
ul{...}
p{..}

AVOID STYLING ELEMENTS
unless deﬁning defaults

div{...}
X
ul{...}
p{..}

AVOID STYLING ELEMENTS
unless deﬁning defaults
.error{...}
.section{...}
.products{...}

.myModule .inner b{...}
.myModule2 b {...}

GIVE RULES THE
SAME STRENGTH
Use cascade order to overwrite previous rules

X
.myModule .inner b{...}
.myModule2 b {...}

GIVE RULES THE
SAME STRENGTH
Use cascade order to overwrite previous rules

.myModule b{...}
.myModule2 b {...}

.sidebar ul{...}
.header ul {...}

AVOID SPECIFYING
LOCATION
Apply classes to the object you wish to change

X
.sidebar ul{...}
.header ul {...}

AVOID SPECIFYING
LOCATION
Apply classes to the object you wish to change

.mainNav{...}
.subNav {...}

AVOID OVERLY SPECIFIC
CLASSES
they’re all semantic, but limiting

CLASSES

.vehicle{...}
.motorcycle{...}
.ducati{...}
.ducatiMonster620{...}
.nicolesDucatiMonster620{...}

CLASSES

.vehicle{...}
.motorcycle{...}
.ducati{...}

X
.ducatiMonster620{...}
.nicolesDucatiMonster620{...}

#myUniqueIdentifier{...}
#myUniqueIdentifier2{...}

AVOID SINGLETONS
ids can only be used once in any given page

Source: Chris Griego

X
#myUniqueIdentifier{...}
#myUniqueIdentifier2{...}

AVOID SINGLETONS
ids can only be used once in any given page

Source: Chris Griego

Media
Subheading
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna
aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis
aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat
cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

USE MIXINS
to avoid repeating code

Media Extended
Subheading
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna
aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis
aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat
cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

.inner{...} .weatherMod .inner{...}
.tr{...} .weatherMod .tr{...}
.bl{...} .weatherMod .bl{...}

ENCAPSULATION
don’t access sub-nodes of an object directly

inner

.inner{...}
X
.weatherMod .inner{...}
.tr{...} .weatherMod .tr{...}
.bl{...} .weatherMod .bl{...}

ENCAPSULATION
don’t access sub-nodes of an object directly

inner

Taming CSS Selectors

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