(sass) конвертор в em

SassMeister-input.scss

// ----
// Sass (v3.4.9)
// Compass (v1.0.1)
// ----

@function em( $input:null, $em:16 ) {

	$support-num: px em;
	$support-str: auto;
	$output: ();

	@if not $input { @error "#{$input}"; @return null }

	@if not unitless( $em ) {

		$em-unit: unit( $em );

		@if $em-unit == px { $em: $em/1px }
		@else if $em-unit == em { $em: $em/1em*16 }
		@else { @error "#{$em}."; @return null }
	}

	@each $i in $input {
		
		$i-type: type-of( $i );

		@if $i-type == number {

			$i-unit: unit( $i );
			$i-unitless: unitless( $i );
			
			@if not $i-unitless and not index( $support-num, $i-unit ) { @error "( #{$i} )"; @return null }		
			@else if $i == 0 { $i: 0 }
			@else if $i-unitless { $i: $i*1em/$em }
			@else if $i-unit == px { $i: $i/1px*1em/$em }
		}

		@else if $i-type == string {

			@if not index( $support-str, $i ) { @error "( #{$i} )"; @return null }
		}

		$output: append( $output, $i )
	}

	@if length( $output ) == 1 { @return nth( $output, 1 ) }

	@return $output;
}

.a{
  test: em( 2px 3 4em auto, 20px);
}

SassMeister-output.css

.a {
  test: 0.1em 0.15em 4em auto;
}