mirror of
https://github.com/danog/sass-site.git
synced 2024-12-11 17:09:52 +01:00
154 lines
5.1 KiB
Plaintext
154 lines
5.1 KiB
Plaintext
---
|
||
title: Special Functions
|
||
table_of_contents: true
|
||
introduction: >
|
||
CSS defines many functions, and most of them work just fine with Sass’s normal
|
||
function syntax. They’re parsed as function calls, resolved to [plain CSS
|
||
functions](/documentation/at-rules/function#plain-css-functions), and compiled
|
||
as-is to CSS. There are a few exceptions, though, which have special syntax
|
||
that can’t just be parsed as a [SassScript
|
||
expression](/documentation/syntax/structure#expressions). All special function
|
||
calls return [unquoted strings](/documentation/values/strings#unquoted).
|
||
---
|
||
|
||
{% markdown %}
|
||
## `url()`
|
||
|
||
The [`url()` function][] is commonly used in CSS, but its syntax is different
|
||
than other functions: it can take either a quoted *or* unquoted URL. Because an
|
||
unquoted URL isn't a valid SassScript expression, Sass needs special logic to
|
||
parse it.
|
||
|
||
[`url()` function]: https://developer.mozilla.org/en-US/docs/Web/CSS/url
|
||
|
||
If the `url()`'s argument is a valid unquoted URL, Sass parses it as-is,
|
||
although [interpolation][] may also be used to inject SassScript values. If it's
|
||
not a valid unquoted URL—for example, if it contains [variables][] or [function
|
||
calls][]—it's parsed as a normal [plain CSS function call][].
|
||
|
||
[interpolation]: /documentation/interpolation
|
||
[variables]: /documentation/variables
|
||
[function calls]: /documentation/at-rules/function
|
||
[plain CSS function call]: /documentation/at-rules/function#plain-css-functions
|
||
{% endmarkdown %}
|
||
|
||
{% codeExample 'url' %}
|
||
$roboto-font-path: "../fonts/roboto";
|
||
|
||
@font-face {
|
||
// This is parsed as a normal function call that takes a quoted string.
|
||
src: url("#{$roboto-font-path}/Roboto-Thin.woff2") format("woff2");
|
||
|
||
font-family: "Roboto";
|
||
font-weight: 100;
|
||
}
|
||
|
||
@font-face {
|
||
// This is parsed as a normal function call that takes an arithmetic
|
||
// expression.
|
||
src: url($roboto-font-path + "/Roboto-Light.woff2") format("woff2");
|
||
|
||
font-family: "Roboto";
|
||
font-weight: 300;
|
||
}
|
||
|
||
@font-face {
|
||
// This is parsed as an interpolated special function.
|
||
src: url(#{$roboto-font-path}/Roboto-Regular.woff2) format("woff2");
|
||
|
||
font-family: "Roboto";
|
||
font-weight: 400;
|
||
}
|
||
===
|
||
$roboto-font-path: "../fonts/roboto"
|
||
|
||
@font-face
|
||
// This is parsed as a normal function call that takes a quoted string.
|
||
src: url("#{$roboto-font-path}/Roboto-Thin.woff2") format("woff2")
|
||
|
||
font-family: "Roboto"
|
||
font-weight: 100
|
||
|
||
|
||
@font-face
|
||
// This is parsed as a normal function call that takes an arithmetic
|
||
// expression.
|
||
src: url($roboto-font-path + "/Roboto-Light.woff2") format("woff2")
|
||
|
||
font-family: "Roboto"
|
||
font-weight: 300
|
||
|
||
|
||
@font-face
|
||
// This is parsed as an interpolated special function.
|
||
src: url(#{$roboto-font-path}/Roboto-Regular.woff2) format("woff2")
|
||
|
||
font-family: "Roboto"
|
||
font-weight: 400
|
||
{% endcodeExample %}
|
||
|
||
{{ '## `element()`, `progid:...()`, and `expression()`' | markdown }}
|
||
|
||
{% # Arguments are (in order): `dart`, `libsass`, `node`, `ruby`, optional feature name, additional details within %}
|
||
{% compatibility "<1.40.0", false, null, false, "calc()" %}
|
||
LibSass, Ruby Sass, and versions of Dart Sass prior to 1.40.0 parse `calc()` as
|
||
special syntactic function like `element()`.
|
||
|
||
Dart Sass versions 1.40.0 and later parse `calc()` as a [calculation].
|
||
|
||
[calculation]: /documentation/values/calculations
|
||
{% endcompatibility %}
|
||
|
||
{% # Arguments are (in order): `dart`, `libsass`, `node`, `ruby`, optional feature name, additional details within %}
|
||
{% compatibility ">=1.31.0 <1.40.0", false, null, false, "clamp()" %}
|
||
LibSass, Ruby Sass, and versions of Dart Sass prior to 1.31.0 parse `clamp()` as
|
||
a [plain CSS function] rather than supporting special syntax within it.
|
||
|
||
[plain CSS function]: /documentation/at-rules/function#plain-css-functions
|
||
|
||
Dart Sass versions between 1.31.0 and 1.40.0 parse `clamp()` as special
|
||
syntactic function like `element()`.
|
||
|
||
Dart Sass versions 1.40.0 and later parse `clamp()` as a [calculation].
|
||
|
||
[calculation]: /documentation/values/calculations
|
||
{% endcompatibility %}
|
||
|
||
{% markdown %}
|
||
The [`element()`] function is defined in the CSS spec, and because its IDs could
|
||
be parsed as colors, they need special parsing.
|
||
|
||
[`element()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/element
|
||
|
||
[`expression()`][] and functions beginning with [`progid:`][] are legacy
|
||
Internet Explorer features that use non-standard syntax. Although they're no
|
||
longer supported by recent browsers, Sass continues to parse them for backwards
|
||
compatibility.
|
||
|
||
[`expression()`]: https://blogs.msdn.microsoft.com/ie/2008/10/16/ending-expressions/
|
||
[`progid:`]: https://blogs.msdn.microsoft.com/ie/2009/02/19/the-css-corner-using-filters-in-ie8/
|
||
|
||
Sass allows *any text* in these function calls, including nested parentheses.
|
||
Nothing is interpreted as a SassScript expression, with the exception that
|
||
[interpolation][] can be used to inject dynamic values.
|
||
|
||
[interpolation]: /documentation/interpolation
|
||
{% endmarkdown %}
|
||
|
||
{% codeExample 'element' %}
|
||
$logo-element: logo-bg;
|
||
|
||
.logo {
|
||
background: element(##{$logo-element});
|
||
}
|
||
===
|
||
$logo-element: logo-bg
|
||
|
||
.logo
|
||
background: element(##{$logo-element})
|
||
===
|
||
.logo {
|
||
background: element(#logo-bg);
|
||
}
|
||
{% endcodeExample %}
|