mirror of
https://github.com/danog/sass-site.git
synced 2024-12-14 10:28:05 +01:00
217 lines
8.1 KiB
Plaintext
217 lines
8.1 KiB
Plaintext
---
|
|
title: Strings
|
|
table_of_contents: true
|
|
introduction: >
|
|
Strings are sequences of characters (specifically [Unicode code
|
|
points](https://en.wikipedia.org/wiki/Code_point)). Sass supports two kinds of
|
|
strings whose internal structure is the same but which are rendered
|
|
differently: [quoted strings](#quoted), like `"Helvetica Neue"`, and [unquoted
|
|
strings](#unquoted) (also known as *identifiers*), like `bold`. Together,
|
|
these cover the different kinds of text that appear in CSS.
|
|
---
|
|
|
|
<% fun_fact do %>
|
|
You can convert a quoted string to an unquoted string using the [`unquote()`
|
|
function][], and you can convert an unquoted string to a quoted string using
|
|
the [`quote()` function][].
|
|
|
|
[`unquote()` function]: ../functions/string#unquote
|
|
[`quote()` function]: ../functions/string#quote
|
|
|
|
<% example(autogen_css: false) do %>
|
|
@debug unquote(".widget:hover"); // .widget:hover
|
|
@debug quote(bold); // "bold"
|
|
===
|
|
@debug unquote(".widget:hover") // .widget:hover
|
|
@debug quote(bold) // "bold"
|
|
<% end %>
|
|
<% end %>
|
|
|
|
## Escapes
|
|
|
|
All Sass strings support the standard CSS [escape codes][]:
|
|
|
|
[escape codes]: https://developer.mozilla.org/en-US/docs/Web/CSS/string#Syntax
|
|
|
|
* Any character other than a letter from A to F or a number from 0 to 9 (even a
|
|
newline!) can be included as part of a string by writing `\` in front of it.
|
|
|
|
* Any character can be included as part of a string by writing `\` followed by
|
|
its [Unicode code point number][] written in [hexadecimal][]. You can
|
|
optionally include a space after the code point number to indicate where the
|
|
Unicode number ends.
|
|
|
|
[Unicode code point number]: https://en.wikipedia.org/wiki/List_of_Unicode_characters
|
|
[hexadecimal]: https://en.wikipedia.org/wiki/Hexadecimal
|
|
|
|
<% example(autogen_css: false) do %>
|
|
@debug "\""; // '"'
|
|
@debug \.widget; // \.widget
|
|
@debug "\a"; // "\a" (a string containing only a newline)
|
|
@debug "line1\a line2"; // "line1\a line2"
|
|
@debug "Nat + Liz \1F46D"; // "Nat + Liz 👭"
|
|
===
|
|
@debug "\"" // '"'
|
|
@debug \.widget // \.widget
|
|
@debug "\a" // "\a" (a string containing only a newline)
|
|
@debug "line1\a line2" // "line1\a line2" (foo and bar are separated by a newline)
|
|
@debug "Nat + Liz \1F46D" // "Nat + Liz 👭"
|
|
<% end %>
|
|
|
|
<% fun_fact do %>
|
|
For characters that are allowed to appear in strings, writing the Unicode
|
|
escape produces exactly the same string as writing the character itself.
|
|
<% end %>
|
|
|
|
## Quoted
|
|
|
|
Quoted strings are written between either single or double quotes, as in
|
|
`"Helvetica Neue"`. They can contain [interpolation][], as well as any unescaped
|
|
character except for:
|
|
|
|
[interpolation]: ../interpolation
|
|
|
|
* `\`, which can be escaped as `\\`;
|
|
* `'` or `"`, whichever was used to define that string, which can be escaped as
|
|
`\'` or `\"`;
|
|
* newlines, which can be escaped as `\a ` (including a trailing space).
|
|
|
|
Quoted strings are guaranteed to be compiled to CSS strings that have the same
|
|
contents as the original Sass strings. The exact format may vary based on the
|
|
implementation or configuration—a string containing a double quote may be
|
|
compiled to `"\""` or `'"'`, and a non-[ASCII][] character may or may not be
|
|
escaped. But that should be parsed the same in any standards-compliant CSS
|
|
implementation, including all browsers.
|
|
|
|
[ASCII]: https://en.wikipedia.org/wiki/ASCII
|
|
|
|
<% example(autogen_css: false) do %>
|
|
@debug "Helvetica Neue"; // "Helvetica Neue"
|
|
@debug "C:\\Program Files"; // "C:\\Program Files"
|
|
@debug "\"Don't Fear the Reaper\""; // "\"Don't Fear the Reaper\""
|
|
@debug "line1\a line2"; // "line1\a line2"
|
|
|
|
$roboto-variant: "Mono";
|
|
@debug "Roboto #{$roboto-variant}"; // "Roboto Mono"
|
|
===
|
|
@debug "Helvetica Neue" // "Helvetica Neue"
|
|
@debug "C:\\Program Files" // "C:\\Program Files"
|
|
@debug "\"Don't Fear the Reaper\"" // "\"Don't Fear the Reaper\""
|
|
@debug "line1\a line2" // "line1\a line2"
|
|
|
|
$roboto-variant: "Mono"
|
|
@debug "Roboto #{$roboto-variant}" // "Roboto Mono"
|
|
<% end %>
|
|
|
|
<% fun_fact do %>
|
|
When a quoted string is injected into another value via interpolation, [its
|
|
quotes are removed][]! This makes it easy to write strings containing
|
|
selectors, for example, that can be injected into style rules without adding
|
|
quotes.
|
|
|
|
[its quotes are removed]: ../interpolation#quoted-strings
|
|
<% end %>
|
|
|
|
## Unquoted
|
|
|
|
Unquoted strings are written as CSS [identifiers][], following the syntax
|
|
diagram below. They may include [interpolation][] anywhere.
|
|
|
|
[identifiers]: https://drafts.csswg.org/css-syntax-3/#ident-token-diagram
|
|
|
|
<figure>
|
|
<object type="image/svg+xml" data="/assets/img/illustrations/identifier-diagram.svg"></object>
|
|
<figcaption class="copyright">Railroad diagram copyright © 2018 W3C<sup>®</sup> (MIT, ERCIM, Keio, Beihang). W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/2015/copyright-software-and-document">permissive document license</a> rules apply.
|
|
</figcaption>
|
|
|
|
<% example do %>
|
|
@debug bold; // bold
|
|
@debug -webkit-flex; // -webkit-flex
|
|
@debug --123; // --123
|
|
|
|
$prefix: ms;
|
|
@debug -#{$prefix}-flex; // -ms-flex
|
|
===
|
|
@debug bold // bold
|
|
@debug -webkit-flex // -webkit-flex
|
|
@debug --123 // --123
|
|
|
|
$prefix: ms
|
|
@debug -#{$prefix}-flex // -ms-flex
|
|
<% end %>
|
|
|
|
<% heads_up do %>
|
|
Not all identifiers are parsed as unquoted strings:
|
|
|
|
* [CSS color names][] are parsed as [colors][].
|
|
* `null` is parsed as [Sass's `null` value][].
|
|
* `true` and `false` are parsed as [Booleans][].
|
|
* `not`, `and`, and `or` are parsed as [Boolean operators][].
|
|
|
|
[CSS color names]: https://developer.mozilla.org/en-US/docs/Web/CSS/color_value#Color_keywords
|
|
[colors]: colors
|
|
[Sass's `null` value]: null
|
|
[Booleans]: booleans
|
|
[Boolean operators]: ../operators/boolean
|
|
|
|
Because of this, it's generally a good idea to write quoted strings unless
|
|
you're specifically writing the value of a CSS property that uses unquoted
|
|
strings.
|
|
<% end %>
|
|
|
|
### Escapes
|
|
|
|
<% impl_status dart: '1.11.0', libsass: false, ruby: false do %>
|
|
LibSass, Ruby Sass, and older versions of Dart Sass don't normalize escapes in
|
|
identifiers. Instead, the text in the unquoted string is the exact text the
|
|
user wrote. For example, `\1F46D` and `👭` are not considered equivalent.
|
|
<% end %>
|
|
|
|
When an unquoted string is parsed, the literal text of escapes are parsed as
|
|
part of the string. For example, `\a ` is parsed as the characters `\`, `a`, and
|
|
space. In order to ensure that unquoted strings that have the same meanings in
|
|
CSS are parsed the same way, though, these escapes are *normalized*. For each
|
|
code point, whether it's escaped or unescaped:
|
|
|
|
* If it's a valid identifier character, it's included unescaped in the unquoted
|
|
string. For example, `\1F46D` returns the unquoted string `👭`.
|
|
|
|
* If it's a printable character other than a newline or a tab, it's included
|
|
after a `\`. For example, `\21 ` returns the unquoted string `\!`.
|
|
|
|
* Otherwise, the lowercase Unicode escape is included with a trailing space. For
|
|
example, `\7Fx` returns the unquoted string `\7f x`.
|
|
|
|
<% example do %>
|
|
@debug \1F46D; // 👭
|
|
@debug \21; // \!
|
|
@debug \7Fx; // \7f x
|
|
@debug str-length(\7Fx); // 5
|
|
===
|
|
@debug \1F46D // 👭
|
|
@debug \21 // \!
|
|
@debug \7Fx // \7f x
|
|
@debug str-length(\7Fx) // 5
|
|
<% end %>
|
|
|
|
## String Indexes
|
|
|
|
Sass has a number of [string functions][] that take or return numbers, called
|
|
*indexes*, that refer to the characters in a string. The index 1 indicates the
|
|
first character of the string. Note that this is different than many programming
|
|
languages where indexes start at 0! Sass also makes it easy to refer to the end
|
|
of a string. The index -1 refers to the last character in a string, -2 refers to
|
|
the second-to-last, and so on.
|
|
|
|
[string functions]: ../functions/string
|
|
|
|
<% example do %>
|
|
@debug str-index("Helvetica Neue", "Helvetica"); // 1
|
|
@debug str-index("Helvetica Neue", "Neue"); // 11
|
|
@debug str-slice("Roboto Mono", -4); // "Mono"
|
|
===
|
|
@debug str-index("Helvetica Neue", "Helvetica") // 1
|
|
@debug str-index("Helvetica Neue", "Neue") // 11
|
|
@debug str-slice("Roboto Mono", -4) // "Mono"
|
|
<% end %>
|