Merge pull request #464 from dmethvin/fix-10021-relative-negative-values

Fixes #10021. Allow negative relative values for `.css()` 

1 files changed, 8 insertions, 9 deletions

diff --git a/src/css.js b/src/css.js
index efd881653..a4ca555ef 100644
--- a/src/css.js
+++ b/src/css.js
@@ -6,8 +6,7 @@ var ralpha = /alpha\([^)]*\)/i,
 	rupper = /([A-Z]|^ms)/g,
 	rnumpx = /^-?\d+(?:px)?$/i,
 	rnum = /^-?\d/,
-	rrelNum = /^[+\-]=/,
-	rrelNumFilter = /[^+\-\.\de]+/g,
+	rrelNum = /^([-+])=([-+.\de]+)/,
 
 	cssShow = { position: "absolute", visibility: "hidden", display: "block" },
 	cssWidth = [ "Left", "Right" ],
@@ -84,18 +83,18 @@ jQuery.extend({
 		if ( value !== undefined ) {
 			type = typeof value;
 
-			// Make sure that NaN and null values aren't set. See: #7116
-			if ( type === "number" && isNaN( value ) || value == null ) {
-				return;
-			}
-
 			// convert relative number strings (+= or -=) to relative numbers. #7345
-			if ( type === "string" && rrelNum.test( value ) ) {
-				value = +value.replace( rrelNumFilter, "" ) + parseFloat( jQuery.css( elem, name ) );
+			if ( type === "string" && (ret = rrelNum.exec( value )) ) {
+				value = ( +( ret[1] + 1) * +ret[2] ) + parseFloat( jQuery.css( elem, name ) );
 				// Fixes bug #9237
 				type = "number";
 			}
 
+			// Make sure that NaN and null values aren't set. See: #7116
+			if ( value == null || type === "number" && isNaN( value ) ) {
+				return;
+			}
+
 			// If a number was passed in, add 'px' to the (except for certain CSS properties)
 			if ( type === "number" && !jQuery.cssNumber[ origName ] ) {
 				value += "px";