Sass meta.call() Function

What You’ll Learn

meta.call() belongs to the built-in sass:meta module. It invokes a function value with arguments and returns the result. This page covers meta.get-function, higher-order helpers, the deprecated string form, vs meta.apply, and five compiled examples.

What Is meta.call()?

Normally you write math.pow(2, 8) with the function name fixed. Sometimes you want to pass a function into another function—a filter, a mapper, a condition. Sass represents that as a function value. meta.call runs it.

• $function must be a function value (usually from meta.get-function)
• Extra arguments are forwarded to that function
• The return value is whatever the invoked function returns

📝 Syntax

@use "sass:meta";

// Recommended
meta.call($function, $args...)

// Legacy global name (same idea)
call($function, $args...)

Parameters

Return value

📦 Loading sass:meta

// Recommended — namespaced
@use "sass:meta";
@use "sass:math";
$result: meta.call(meta.get-function("abs", $module: "math"), -4);

// Optional — bring members into scope
@use "sass:meta" as *;
$result: call(get-function("abs", $module: "math"), -4);

// Legacy global
$result: call(get-function("abs", $module: "math"), -4);

🔗 Pair with meta.get-function

Official rule: $function must be a function value. Resolve it first:

@use "sass:meta";

@function double($n) {
  @return $n * 2;
}

$fn: meta.get-function("double");
$value: meta.call($fn, 21); // 42

• meta.get-function($name) — current module
• meta.get-function($name, $module: "ns") — from a @use namespace

⚠️ Deprecated: String Names

Older LibSass / Ruby Sass accepted call("function-name", …). That still works for compatibility, but Sass docs mark it deprecated because modules mean a name may not be globally unique.

📋 meta.call vs meta.apply

🛠 Compatibility

This is about Sass compilers, not browsers. The call runs at compile time.

Prefer current Dart Sass and function values via meta.get-function.

Examples Gallery

Each example uses function values (not deprecated strings). Open View Compiled CSS for verified Dart Sass output.

@use "sass:meta";

@function double($n) {
  @return $n * 2;
}

$fn: meta.get-function("double");

.box {
  width: meta.call($fn, 60px);
}

.box {
  width: 120px;
}

@use "sass:list";
@use "sass:meta";
@use "sass:string";

@function remove-where($list, $condition) {
  $new-list: ();
  $separator: list.separator($list);
  @each $element in $list {
    @if not meta.call($condition, $element) {
      $new-list: list.append($new-list, $element, $separator: $separator);
    }
  }
  @return $new-list;
}

$fonts: Tahoma, Geneva, "Helvetica Neue", Helvetica, Arial, sans-serif;

.content {
  @function contains-helvetica($string) {
    @return string.index($string, "Helvetica");
  }
  font-family: remove-where($fonts, meta.get-function("contains-helvetica"));
}

.content {
  font-family: Tahoma, Geneva, Arial, sans-serif;
}

@use "sass:math";
@use "sass:meta";

$pow: meta.get-function("pow", $module: "math");

.scale {
  --eight: #{meta.call($pow, 2, 3)};
  width: meta.call($pow, 2, 4) * 1px;
}

.scale {
  --eight: 8;
  width: 16px;
}

@use "sass:color";
@use "sass:meta";

@function make-darker($c, $amount) {
  @return color.adjust($c, $lightness: -$amount);
}

@function make-lighter($c, $amount) {
  @return color.adjust($c, $lightness: $amount);
}

$mode: "darken";
$adjust: if(
  $mode == "darken",
  meta.get-function("make-darker"),
  meta.get-function("make-lighter")
);

.btn {
  background: meta.call($adjust, #3b82f6, 15%);
}

.btn {
  background: #0a59da;
}

@use "sass:list";
@use "sass:meta";

@function scale-space($n) {
  @return $n * 1.25;
}

@function map-call($list, $fn) {
  $out: ();
  @each $item in $list {
    $out: list.append($out, meta.call($fn, $item));
  }
  @return $out;
}

$spaces: 4px, 8px, 16px;
$scaled: map-call($spaces, meta.get-function("scale-space"));

.stack {
  gap: list.nth($scaled, 2);
}

.stack {
  gap: 10px;
}

🚀 Real-World Use Cases

• Higher-order helpers — filters, mappers, and reducers over lists (official remove-where).
• Theme adjusters — choose make-darker / make-lighter (or similar helpers) from config, then call once.
• Module bridging — invoke sass:math / sass:color members via get-function + $module.
• Plugin APIs — accept a function value from consumers instead of a fixed name.
• Migration off string call() — replace deprecated call("name", …) safely.

⚠️ Common Pitfalls

• String first argument — deprecated; resolve with meta.get-function first.
• Confusing with meta.apply — functions return values; mixins emit CSS.
• Wrong arity — argument count must match the target function.
• Missing $module — built-ins from sass:math need the namespace when using get-function.
• Expecting runtime JS callbacks — everything resolves when Sass compiles.

💡 Best Practices