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180 lines
4.5 KiB
Plaintext
180 lines
4.5 KiB
Plaintext
---
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title: Style Rules
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table_of_contents: true
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introduction: >
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Style rules are the foundation of Sass, just like they are for CSS. And they
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work the same way: you choose which elements to style with a selector, and
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[declare properties](/documentation/style-rules/declarations) that affect how
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those elements look.
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---
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{% codeExample 'style-rules' %}
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.button {
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padding: 3px 10px;
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font-size: 12px;
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border-radius: 3px;
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border: 1px solid #e1e4e8;
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}
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===
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.button
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padding: 3px 10px
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font-size: 12px
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border-radius: 3px
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border: 1px solid #e1e4e8
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{% endcodeExample %}
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{% markdown %}
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## Nesting
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But Sass wants to make your life easier. Rather than repeating the same
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selectors over and over again, you can write one style rules inside another.
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Sass will automatically combine the outer rule's selector with the inner
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rule's.
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{% endmarkdown %}
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{% render 'code_snippets/example-nesting' %}
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{% headsUp %}
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Nested rules are super helpful, but they can also make it hard to visualize
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how much CSS you're actually generating. The deeper you nest, the more
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bandwidth it takes to serve your CSS and the more work it takes the browser to
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render it. Keep those selectors shallow!
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{% endheadsUp %}
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{% markdown %}
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### Selector Lists
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Nested rules are clever about handling selector lists (that is,
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comma-separated selectors). Each complex selector (the ones between the
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commas) is nested separately, and then they're combined back into a selector
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list.
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{% endmarkdown %}
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{% codeExample 'selector-lists' %}
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.alert, .warning {
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ul, p {
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margin-right: 0;
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margin-left: 0;
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padding-bottom: 0;
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}
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}
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===
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.alert, .warning
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ul, p
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margin-right: 0
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margin-left: 0
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padding-bottom: 0
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{% endcodeExample %}
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{% markdown %}
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### Selector Combinators
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You can nest selectors that use [combinators][] as well. You can put the
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combinator at the end of the outer selector, at the beginning of the inner
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selector, or even all on its own in between the two.
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[combinators]: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors#Combinators#Combinators
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{% endmarkdown %}
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{% codeExample 'selector-combinators' %}
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ul > {
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li {
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list-style-type: none;
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}
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}
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h2 {
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+ p {
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border-top: 1px solid gray;
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}
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}
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p {
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~ {
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span {
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opacity: 0.8;
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}
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}
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}
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===
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ul >
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li
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list-style-type: none
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h2
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+ p
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border-top: 1px solid gray
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p
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~
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span
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opacity: 0.8
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{% endcodeExample %}
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{% markdown %}
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### Advanced Nesting
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If you want to do more with your nested style rules than just combine them in
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order with the descendant combinator (that is, a plain space) separating them,
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Sass has your back. See the [parent selector documentation][] for more
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details.
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[parent selector documentation]: /documentation/style-rules/parent-selector
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## Interpolation
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You can use [interpolation][] to inject values from [expressions][] like
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variables and function calls into your selectors. This is particularly useful
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when you're writing [mixins][], since it allows you to create selectors from
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parameters your users pass in.
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[interpolation]: /documentation/interpolation
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[expressions]: /documentation/syntax/structure#expressions
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[mixins]: /documentation/at-rules/mixin
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{% endmarkdown %}
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{% codeExample 'interpolation' %}
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@mixin define-emoji($name, $glyph) {
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span.emoji-#{$name} {
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font-family: IconFont;
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font-variant: normal;
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font-weight: normal;
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content: $glyph;
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}
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}
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@include define-emoji("women-holding-hands", "👭");
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===
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@mixin define-emoji($name, $glyph)
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span.emoji-#{$name}
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font-family: IconFont
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font-variant: normal
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font-weight: normal
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content: $glyph
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@include define-emoji("women-holding-hands", "👭")
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{% endcodeExample %}
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{% funFact %}
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Sass only parses selectors *after* interpolation is resolved. This means you
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can safely use interpolation to generate any part of the selector without
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worrying that it won't parse.
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{% endfunFact %}
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{% markdown %}
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You can combine interpolation with the parent selector `&`, the [`@at-root`
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rule][], and [selector functions][] to wield some serious power when
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dynamically generating selectors. For more information, see the [parent
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selector documentation][].
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[`@at-root` rule]: /documentation/at-rules/at-root
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[selector functions]: /documentation/modules/selector
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[parent selector documentation]: /documentation/style-rules/parent-selector
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{% endmarkdown %}
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