mirror of
https://github.com/danog/sass-site.git
synced 2024-12-12 17:37:36 +01:00
111 lines
4.5 KiB
Markdown
111 lines
4.5 KiB
Markdown
---
|
|
title: Structure of a Stylesheet
|
|
table_of_contents: true
|
|
introduction: >
|
|
Just like CSS, most Sass stylesheets are mainly made up of style rules that
|
|
contain property declarations. But Sass stylesheets have many more features
|
|
that can exist alongside these.
|
|
---
|
|
|
|
## Statements
|
|
|
|
A Sass stylesheet is made up of a series of _statements_, which are evaluated in
|
|
order to build the resulting CSS. Some statements may have _blocks_, defined
|
|
using `{` and `}`, which contain other statements. For example, a style rule is
|
|
a statement with a block. That block contains other statements, such as property
|
|
declarations.
|
|
|
|
In SCSS, statements are separated by semicolons (which are optional if the
|
|
statement uses a block). In the indented syntax, they're just separated by
|
|
newlines.
|
|
|
|
### Universal Statements
|
|
|
|
These types of statements can be used anywhere in a Sass stylesheet:
|
|
|
|
- [Variable declarations](/documentation/variables), like `$var: value`.
|
|
- [Flow control at-rules](/documentation/at-rules/control), like `@if` and
|
|
`@each`.
|
|
- The [`@error`](/documentation/at-rules/error),
|
|
[`@warn`](/documentation/at-rules/warn), and
|
|
[`@debug`](/documentation/at-rules/debug) rules.
|
|
|
|
### CSS Statements
|
|
|
|
These statements produce CSS. They can be used anywhere except within a
|
|
`@function`:
|
|
|
|
- [Style rules](/documentation/style-rules), like `h1 { /* ... */ }`.
|
|
- [CSS at-rules](/documentation/at-rules/css), like `@media` and `@font-face`.
|
|
- [Mixin uses](/documentation/at-rules/mixin) using `@include`.
|
|
- The [`@at-root` rule](/documentation/at-rules/at-root).
|
|
|
|
### Top-Level Statements
|
|
|
|
These statements can only be used at the top level of a stylesheet, or nested
|
|
within a CSS statement at the top level:
|
|
|
|
- [Module loads](/documentation/at-rules/use), using `@use`.
|
|
- [Imports](/documentation/at-rules/import), using `@import`.
|
|
- [Mixin definitions](/documentation/at-rules/mixin) using `@mixin`.
|
|
- [Function definitions](/documentation/at-rules/function) using `@function`.
|
|
|
|
### Other Statements
|
|
|
|
- [Property declarations](/documentation/style-rules/declarations) like `width:
|
|
100px` may only be used within style rules and some CSS at-rules.
|
|
- The [`@extend` rule](/documentation/at-rules/extend) may only be used within
|
|
style rules.
|
|
|
|
## Expressions
|
|
|
|
An _expression_ is anything that goes on the right-hand side of a property or
|
|
variable declaration. Each expression produces a _[value][]_. Any valid CSS
|
|
property value is also a Sass expression, but Sass expressions are much more
|
|
powerful than plain CSS values. They're passed as arguments to [mixins][] and
|
|
[functions][], used for control flow with the [`@if` rule][], and manipulated
|
|
using [arithmetic][]. We call Sass's expression syntax _SassScript_.
|
|
|
|
[value]: /documentation/values
|
|
[mixins]: /documentation/at-rules/mixin
|
|
[functions]: /documentation/at-rules/function
|
|
[`@if` rule]: /documentation/at-rules/control/if
|
|
[arithmetic]: /documentation/operators/numeric
|
|
|
|
### Literals
|
|
|
|
The simplest expressions just represent static values:
|
|
|
|
- [Numbers](/documentation/values/numbers), which may or may not have units,
|
|
like `12` or `100px`.
|
|
- [Strings](/documentation/values/strings), which may or may not have quotes,
|
|
like `"Helvetica Neue"` or `bold`.
|
|
- [Colors](/documentation/values/colors), which can be referred to by their hex
|
|
representation or by name, like `#c6538c` or `blue`.
|
|
- The [boolean](/documentation/values/booleans) literals `true` or `false`.
|
|
- The singleton [`null`](/documentation/values/null).
|
|
- [Lists of values](/documentation/values/lists), which may be separated by
|
|
spaces or commas and which may be enclosed in square brackets or no brackets
|
|
at all, like `1.5em 1em 0 2em`, `Helvetica, Arial, sans-serif`, or
|
|
`[col1-start]`.
|
|
- [Maps](/documentation/values/maps) that associate values with keys, like
|
|
`("background": red, "foreground": pink)`.
|
|
|
|
### Operations
|
|
|
|
Sass defines syntax for a number of operations:
|
|
|
|
{% render 'doc_snippets/operator-list', parens: true %}
|
|
|
|
### Other Expressions
|
|
|
|
- [Variables](/documentation/variables), like `$var`.
|
|
- [Function calls](/documentation/at-rules/function), like `nth($list, 1)` or
|
|
`var(--main-bg-color)`, which may call Sass core library functions or
|
|
user-defined functions, or which may be compiled directly to CSS.
|
|
- [Special functions](/documentation/syntax/special-functions), like
|
|
`calc(1px + 100%)` or `url(http://myapp.com/assets/logo.png)`, that have their
|
|
own unique parsing rules.
|
|
- [The parent selector](/documentation/style-rules/parent-selector), `&`.
|
|
- The value `!important`, which is parsed as an unquoted string.
|