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%Pattern Placeholders Jaime Caballero - LDN Sass #2 GIF Source: giphy.com 21/01/2015

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hi, I’m jaime

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jamie james jiame jaime

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• spanish • frontend architect • sass lover

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this is me when I’m using Sass

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this is me when somebody hands me over vanilla CSS

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me gusta • SMACSS • OOCSS • DRYCSS • BEM

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I worry a lot about keeping my CSS scalable and organised

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this is me going through my CSS workflow

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let’s talk about @extend 1.

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@extend combines selectors

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.foo

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.foo{ color: black; }

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.another

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.another{ color: black; }

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.another{ @extend .foo; }

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.another{ @extend .foo; background: white; }

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.foo, .another{ color: black; } .another{
 background: white;
 }

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combining selectors means no repeating CSS chunks

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this is me when I discovered @extend

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BUT!

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we can’t extend without a selector, can we?

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.foo{ color: black; }

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introducing placeholder selectors 2.

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if you don’t @extend them, they will not be in the CSS

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.foo

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%foo

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%foo{ color: black; }

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you can have anything in one place, ready to use

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BUT!

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i’m not here to say @extend FTW

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all this has its limitations

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you can’t extend in a @media query

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%foo{ color: black; } @media (min-width: 20em){ .another{ @extend %foo; } }

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you can easily get 
 loads of selectors

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a.icon-listen-bl:hover, .event-related .box-title a:hover, .category-related .box-title a:hover, .readmore a:hover, .footer a:hover, .pagination a:hover, .news a:hover, .latest-tweet .date a:hover, .feature .box-header .title a:hover, .caption .title a:hover, .full-agenda-link a:hover,

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that was 46 selectors for 1 property

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i like to call this aggressive extending

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this is me when i see any of it

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we are the problem 3.

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people are complaining

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BUT!

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we are the ones extending the wrong way

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we have to think outside the box

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embrace these limitations

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you can’t extend in a @media query?

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but you can put a media query in a placeholder

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%foo{ color: black; } @media (min-width: 20em){ .another{ @extend .foo; } }

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%foo{ }

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%foo{ @media (min-width: 20em){ } }

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%foo{ @media (min-width: 20em){ color: black; } }

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%foo{ @media (min-width: 20em){ color: black; } } .another{ @extend %foo; }

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@media (min-width: 20em){ .another{ color: black; } }

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implement placeholder patterns

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%nav-fixed{…} %nav-offcanvas{…} %nav-footeranch{…} .nav{
 @extend %nav-fixed;
 }

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%nav-fixed{…} %nav-offcanvas{…} %nav-footeranch{…} .nav{
 @extend %nav-offcanvas;
 }

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%nav-fixed{…} %nav-offcanvas{…} %nav-footeranch{…} .nav{
 @extend %nav-footeranch;
 }

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placeholders for everything

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%foo{…} %foo--good{…} %foo--bad{…}

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combine them

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.Foo.is-good{
 @extend %foo; @extend %foo--good;
 }

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separate them

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.Foo{ @extend %foo; } .is-good{ @extend %foo--good;
 }

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BEM? SUITCSS?
 whatever works

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placeholder patterns add another abstraction layer

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you can create naming-agnostic CSS systems

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when you only use placeholders

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it’s easier to notice a repeated/wrong pattern

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.button--action{
 @extend %btn; @extend %btn--big; @extend %bg--green;
 }

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BUT!

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what about agressive extending
 ?

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agressive extending: fixed 4.

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what if we could 
 limit the amount of selectors
 ?

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actually, we need to set a selector budget

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a warning when we don’t extend properly

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a weekend after 
 (last weekend)

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this is me after last weekend

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jaicab.com/ext/

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the ext(); mixin sets a selector budget and warns you (@warn) when you are:

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extending too much

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extending the same pair (selector, placeholder)
 more than once

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extending twice doesn’t affect your CSS, but it is a bad organisation practise

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this is how it works

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&

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html, .foo, .another

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$selectors: &;

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getting started

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bower install ext

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@import the _ext.scss file into your project

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set your selector budget

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$ext-budget: ( total: 15 );

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it only works with placeholders

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use ext(placeholder);

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%foo{ color: black; } .another{ @include ext(foo); }

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go nuts!

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is @warn not enough?

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enable debug mode

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add ext-debug(); after all your
 @imports

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set a targeted budget

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$ext-budget: ( total: 15, heading: 12 );

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want to see more? change the options

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$ext-options: ( warn-over: true, warn-duplicates: true, over-only: true, show-all: true );

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there’s much more

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but enough for today

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go to 
 github.com/jaicab/ext/

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play with it open an issue send me a pull request fire me a tweet

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thank you! jaicab.com/ext/ @jaicab_ Links: http://bit.ly/1JeTmtr