src/css/curCSS.js

define( [
	"../core",
	"../core/isAttached",
	"./var/rboxStyle",
	"./var/rnumnonpx",
	"./var/getStyles",
	"./var/rcustomProp",
	"../var/rtrimCSS",
	"./support"
], function( jQuery, isAttached, rboxStyle, rnumnonpx, getStyles,
	rcustomProp, rtrimCSS, support ) {

"use strict";

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

		// Support: Firefox 51+
		// Retrieving style before computed somehow
		// fixes an issue with getting wrong values
		// on detached elements
		style = elem.style;

	computed = computed || getStyles( elem );

	// getPropertyValue is needed for:
	//   .css('filter') (IE 9 only, trac-12537)
	//   .css('--customProperty) (gh-3144)
	if ( computed ) {

		// 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+, Chrome <=105+
			// Spec requires trimming whitespace for custom properties (gh-4926).
			// Firefox only trims leading whitespace. Chrome just collapses
			// both leading & trailing whitespace to a single space.
			//
			// 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 );
		}

		// A tribute to the "awesome hack by Dean Edwards"
		// Android Browser returns percentage for some values,
		// but width seems to be reliably pixels.
		// This is against the CSSOM draft spec:
		// https://drafts.csswg.org/cssom/#resolved-values
		if ( !support.pixelBoxStyles() && rnumnonpx.test( ret ) && rboxStyle.test( name ) ) {

			// Remember the original values
			width = style.width;
			minWidth = style.minWidth;
			maxWidth = style.maxWidth;

			// Put in the new values to get a computed value out
			style.minWidth = style.maxWidth = style.width = ret;
			ret = computed.width;

			// Revert the changed values
			style.width = width;
			style.minWidth = minWidth;
			style.maxWidth = maxWidth;
		}
	}

	return ret !== undefined ?

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

return curCSS;
} );