tidy up fix for #3981, thanks matt kruse

diff --git a/src/css.js b/src/css.js
index 12f9d51..973462b 100644 (file)
--- a/src/css.js
+++ b/src/css.js
@@ -123,15 +123,9 @@ jQuery.extend({
                var ret, style = elem.style, filter;
 
                // IE uses filters for opacity
-               if ( !jQuery.support.opacity && name == "opacity" ) {
-                       filter = (filter = style.filter) && filter.indexOf("opacity=") >= 0 ?
-                               filter :
-                               (filter = elem.currentStyle[ 'filter' ]) && filter.indexOf("opacity=") >= 0 ?
-                                       filter :
-                                       null;
-
-                       ret = filter && filter.indexOf("opacity=") >= 0 ?
-                               (parseFloat( filter.match(/opacity=([^)]*)/)[1] ) / 100) + '':
+               if ( !jQuery.support.opacity && name === "opacity" && elem.currentStyle ) {
+                       ret = (elem.currentStyle.filter || "").match(/opacity=([^)]*)/) ?
+                               (parseFloat(RegExp.$1) / 100) + "" :
                                "";
 
                        return ret === "" ?