meta.function-exists($name, $module: null) returns a boolean: whether a function named $name is defined—either as a built-in or a user-defined function. Load it with @use "sass:meta".
meta.function-exists("div", $module: "math") → true · meta.function-exists("scale-color") → true · meta.function-exists("add") → false until you define @function add.
$module for namespaces.After @use "sass:math", check module members with $module: "math". The $module value can also be a module value.
To run the function, use meta.get-function plus meta.call.
@use "sass:meta";
@use "sass:math";
meta.function-exists($name, $module: null); //=> boolean
meta.function-exists("div", $module: "math"); // true
meta.function-exists("scale-color"); // true
meta.function-exists("add"); // false (until defined)
// Global alias (legacy): function-exists($name)
// Prefer meta.function-exists after @use "sass:meta"Pattern: choose a name (and optional module) → check function-exists → branch or call get-function.
$moduleHow lookups work:
| Call | Looks in | Example |
|---|---|---|
meta.function-exists("add") | Current scope / global built-ins (no namespace) | User @function or global built-in |
meta.function-exists("div", $module: "math") | The math @use namespace | math.div |
Before defining add | — | false |
After @function add | Same file / scope | true |
Use meta.mixin-exists for mixins and meta.global-variable-exists for globals. Prefer these over deprecated meta.feature-exists.
Examples use @use "sass:meta". Open View Compiled CSS for verified output (matches official Sass docs samples where shown).
$module)Check a namespaced math helper after @use.
@use "sass:meta";
@use "sass:math";
@debug meta.function-exists("div", $module: "math"); // true
.module-demo {
--div: #{meta.function-exists("div", $module: "math")};
}@use "sass:math" loads the module.$module: "math" scopes the lookup.div exists as math.div.Without $module, Sass checks the un-namespaced name.
@use "sass:meta";
@debug meta.function-exists("scale-color"); // true
.builtin {
--scale: #{meta.function-exists("scale-color")};
}scale-color is found.true.add is false until you define it, then true.
@use "sass:meta";
.before {
--add: #{meta.function-exists("add")}; // false
}
@function add($num1, $num2) {
@return $num1 + $num2;
}
.after {
--add: #{meta.function-exists("add")}; // true
}@function add registers it.true.Branch only when a module function is available.
@use "sass:meta";
@use "sass:math";
.guard {
@if meta.function-exists("div", $module: "math") {
width: math.div(100px, 4);
}
}math.div.25px.get-function / callExists answers yes/no; get-function + call invoke it.
@use "sass:meta";
@use "sass:math";
.pair {
@if meta.function-exists("abs", $module: "math") {
--abs: #{meta.call(meta.get-function("abs", $module: "math"), -8px)};
}
}-8px.Most function-exists bugs are forgetting $module or confusing exists with get-function.
$modulemeta.function-exists("div") is not the same as checking math.div. Pass $module: "math".
A user function only exists after its @function appears for that lookup point.
Use meta.get-function + meta.call to run it.
Use meta.mixin-exists for mixin names.
Prefer the module form with current Dart Sass.
| API | Status |
|---|---|
meta.function-exists() | Dart Sass via @use "sass:meta" |
Global function-exists() | Legacy; no $module parameter—prefer module form |
| Arguments | $name (string), optional $module |
| Return type | Boolean |
Compile with the Dart Sass CLI.
$module for @use namespaces.One line: when you need to know if a function name is defined before using it, call meta.function-exists($name, $module: null).
Practical checklist:
1. @use "sass:meta"
2. Pass the function name as a string
3. Add $module for @use namespaces
4. Branch on the boolean result
5. Use get-function + call to invokeTurn a function name into a value you can pass to meta.call.
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