sass-site/source/documentation/functions/meta.html.md.erb
2018-10-24 15:01:43 -07:00

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---
title: Introspection Functions
---
<% function 'call($function, $args...)' do %>
<%= partial 'documentation/snippets/call-impl-status' %>
Invokes `$function` with `$args` and returns the result.
The `$function` should be a [function][] returned by [`get-function()`][].
[function]: ../values/functions
[`get-function()`]: #get-function
<%= partial 'code-snippets/example-first-class-function' %>
<% end %>
<% function 'content-exists()', returns: 'boolean' do %>
Returns whether the current mixin was passed a [`@content` block][].
[`@content` block]: ../at-rules/mixin#content-blocks
Throws an error if called outside of a mixin.
<% example(autogen_css: false) do %>
@mixin debug-content-exists {
@debug content-exists();
@content;
}
@include debug-content-exists; // false
@include debug-content-exists { // true
// Content!
}
===
@mixin debug-content-exists
@debug content-exists()
@content
@include debug-content-exists // false
@include debug-content-exists // true
// Content!
<% end %>
<% end %>
<% function 'feature-exists($feature)', returns: 'boolean' do %>
Returns whether the current Sass implementation supports `$feature`.
The `$feature` must be a string. The currently recognized features are:
* `global-variable-shadowing`, which means that a local variable will
[shadow][] a global variable unless it has the `!global` flag.
* `extend-selector-pseudoclass`, which means that the [`@extend` rule][] will
affect selectors nested in pseudo-classes like `:not()`.
* `units-level3`, which means that [unit arithmetic][] supports units defined
in [CSS Values and Units Level 3][].
* `at-error`, which means that the [`@error` rule][] is supported.
* `custom-property`, which means that [custom property declaration][] values
don't support any [expressions][] other than [interpolation][].
[shadow]: ../variables#shadowing
[`@extend` rule]: ../at-rules/extend
[unit arithmetic]: ../values/numbers#units
[CSS Values and Units Level 3]: http://www.w3.org/TR/css3-values
[`@error` rule]: ../at-rules/error
[custom property declaration]: ../style-rules/declarations#custom-properties
[expressions]: ../syntax/structure#expressions
[interpolation]: ../interpolation
Returns `false` for any unrecognized `$feature`.
<% example(autogen_css: false) do %>
@debug feature-exists("at-error"); // true
@debug feature-exists("unrecognized"); // false
===
@debug feature-exists("at-error") // true
@debug feature-exists("unrecognized") // false
<% end %>
<% end %>
<% function 'function-exists($name)', returns: 'boolean' do %>
Returns whether a function named `$name` is defined, either as a built-in
function or a user-defined function.
<% example(autogen_css: false) do %>
@debug function-exists("scale-color"); // true
@debug function-exists("add"); // false
@function add($num1, $num2) {
@return $num1 + $num2;
}
@debug function-exists("add"); // true
===
@debug function-exists("scale-color") // true
@debug function-exists("add") // false
@function add($num1, $num2)
@return $num1 + $num2
@debug function-exists("add") // true
<% end %>
<% end %>
<% function 'get-function($name, $css: false)', returns: 'function' do %>
Returns the [function][] named `$name`.
[function]: ../values/functions
This can access both built-in and [user-defined][] functions. By default, it
throws an error if `$name` doesn't refer to either a built-in or user-defined
function. However, if `$css` is `true`, it instead returns a
[plain CSS function][].
[user-defined]: ../at-rules/function
[plain CSS function]: css
The returned function can be called using [`call()`](#call).
<%= partial 'code-snippets/example-first-class-function' %>
<% end %>
<% function 'global-variable-exists($name)', returns: 'boolean' do %>
Returns whether a [global variable][] named `$name` (without the `$`) exists.
[global variable]: ../variables#scope
See also [`variable-exists()`](#variable-exists).
<% example(autogen_css: false) do %>
@debug global-variable-exists("var1"); // false
$var1: value;
@debug global-variable-exists("var1"); // true
h1 {
// $var2 is local.
$var2: value;
@debug global-variable-exists("var2"); // false
}
===
@debug global-variable-exists("var1") // false
$var1: value
@debug global-variable-exists("var1") // true
h1
// $var2 is local.
$var2: value
@debug global-variable-exists("var2") // false
<% end %>
<% end %>
<% function 'inspect($value)', returns: 'unquoted string' do %>
Returns a string representation of `$value`.
Returns a representation of *any* Sass value, not just those that can be
represented in CSS. As such, its return value is not guaranteed to be valid
CSS.
<% heads_up do %>
This function is intended for debugging; its output format is not guaranteed
to be consistent across Sass versions or implementations.
<% end %>
<% example(autogen_css: false) do %>
@debug inspect(10px 20px 30px); // unquote("10px 20px 30px")
@debug inspect(("width": 200px)); // unquote('("width": 200px)')
@debug inspect(null); // unquote("null")
@debug inspect("Helvetica"); // unquote('"Helvetica"')
===
@debug inspect(10px 20px 30px) // unquote("10px 20px 30px")
@debug inspect(("width": 200px)) // unquote('("width": 200px)')
@debug inspect(null) // unquote("null")
@debug inspect("Helvetica") // unquote('"Helvetica"')
<% end %>
<% end %>
<% function 'mixin-exists($name)', returns: 'boolean' do %>
Returns whether a [mixin][] named `$name` exists.
[mixin]: ../at-rules/mixin
<% example(autogen_css: false) do %>
@debug mixin-exists("shadow-none"); // false
@mixin shadow-none {
box-shadow: none;
}
@debug mixin-exists("shadow-none"); // true
===
@debug mixin-exists("shadow-none") // false
@mixin shadow-none
box-shadow: none
@debug mixin-exists("shadow-none") // true
<% end %>
<% end %>
<% function 'type-of($value)', returns: 'unquoted string' do %>
Returns the type of `$value`.
This can return the following values:
* [`number`](../values/numbers)
* [`string`](../values/strings)
* [`color`](../values/colors)
* [`list`](../values/lists)
* [`map`](../values/maps)
* [`bool`](../values/booleans)
* [`null`](../values/null)
* [`function`](../values/functions)
* [`arglist`](../values/lists#argument-lists)
New possible values may be added in the future. It may return either `list` or
`map` for `()`, depending on whether or not it was returned by a
[map function][].
[map function]: map
<% example(autogen_css: false) do %>
@debug type-of(10px); // number
@debug type-of(10px 20px 30px); // list
@debug type-of(()); // list
===
@debug type-of(10px) // number
@debug type-of(10px 20px 30px) // list
@debug type-of(()) // list
<% end %>
<% end %>
<% function 'variable-exists($name)', returns: 'boolean' do %>
Returns whether a variable named `$name` (without the `$`) exists in the
current [scope][].
[scope]: ../variables#scope
See also [`global-variable-exists()`](#global-variable-exists).
<% example(autogen_css: false) do %>
@debug variable-exists("var1"); // false
$var1: value;
@debug variable-exists("var1"); // true
h1 {
// $var2 is local.
$var2: value;
@debug variable-exists("var2"); // true
}
===
@debug variable-exists("var1") // false
$var1: value
@debug variable-exists("var1") // true
h1
// $var2 is local.
$var2: value
@debug variable-exists("var2") // true
<% end %>
<% end %>