---
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 %>