Function curCSS

jquery.js:5800–5855

( elem, name, computed )

}

function curCSS( elem, name, computed ) {
	var ret,
		isCustomProp = rcustomProp.test( name );

	computed = computed || getStyles( elem );

	// getPropertyValue is needed for `.css('--customProperty')` (gh-3144)
	if ( computed ) {

		// A fallback to direct property access is needed as `computed`, being
		// the output of `getComputedStyle`, contains camelCased keys and
		// `getPropertyValue` requires kebab-case ones.
		//
		// Support: IE <=9 - 11+
		// IE only supports `"float"` in `getPropertyValue`; in computed styles
		// it's only available as `"cssFloat"`. We no longer modify properties
		// sent to `.css()` apart from camelCasing, so we need to check both.
		// Normally, this would create difference in behavior: if
		// `getPropertyValue` returns an empty string, the value returned
		// by `.css()` would be `undefined`. This is usually the case for
		// disconnected elements. However, in IE even disconnected elements
		// with no styles return `"none"` for `getPropertyValue( "float" )`
		ret = computed.getPropertyValue( name ) || computed[ name ];

		if ( isCustomProp && ret ) {

			// Support: Firefox 105 - 135+
			// Spec requires trimming whitespace for custom properties (gh-4926).
			// Firefox only trims leading whitespace.
			//
			// Fall back to `undefined` if empty string returned.
			// This collapses a missing definition with property defined
			// and set to an empty string but there's no standard API
			// allowing us to differentiate them without a performance penalty
			// and returning `undefined` aligns with older jQuery.
			//
			// rtrimCSS treats U+000D CARRIAGE RETURN and U+000C FORM FEED
			// as whitespace while CSS does not, but this is not a problem
			// because CSS preprocessing replaces them with U+000A LINE FEED
			// (which *is* CSS whitespace)
			// https://www.w3.org/TR/css-syntax-3/#input-preprocessing
			ret = ret.replace( rtrimCSS, "$1" ) || undefined;
		}

		if ( ret === "" && !isAttached( elem ) ) {
			ret = jQuery.style( elem, name );
		}
	}

	return ret !== undefined ?

		// Support: IE <=9 - 11+
		// IE returns zIndex value as an integer.
		ret + "" :
		ret;
}

var cssPrefixes = [ "Webkit", "Moz", "ms" ],