Added some significant speed-ups to height/width checks, thanks to some code and investigation by Mike Helgeson. Fixes jquery#3082.

Author: jeresig

src/core.js

@@ -734,26 +734,32 @@ jQuery.extend({
 			elem.style[ name ] = old[ name ];
 	},
 
-	css: function( elem, name, force ) {
+	css: function( elem, name, force, extra ) {
 		if ( name == "width" || name == "height" ) {
 			var val, props = { position: "absolute", visibility: "hidden", display:"block" }, which = name == "width" ? [ "Left", "Right" ] : [ "Top", "Bottom" ];
 
 			function getWH() {
 				val = name == "width" ? elem.offsetWidth : elem.offsetHeight;
-				var padding = 0, border = 0;
+
+				if ( extra === "border" )
+					return;
+
 				jQuery.each( which, function() {
-					padding += parseFloat(jQuery.curCSS( elem, "padding" + this, true)) || 0;
-					border += parseFloat(jQuery.curCSS( elem, "border" + this + "Width", true)) || 0;
+					if ( !extra )
+						val -= parseFloat(jQuery.curCSS( elem, "padding" + this, true)) || 0;
+					if ( extra === "margin" )
+						val += parseFloat(jQuery.curCSS( elem, "margin" + this, true)) || 0;
+					else
+						val -= parseFloat(jQuery.curCSS( elem, "border" + this + "Width", true)) || 0;
 				});
-				val -= Math.round(padding + border);
 			}
 
-			if ( jQuery(elem).is(":visible") )
+			if ( elem.offsetWidth !== 0 )
 				getWH();
 			else
 				jQuery.swap( elem, props, getWH );
 
-			return Math.max(0, val);
+			return Math.max(0, Math.round(val));
 		}
 
 		return jQuery.curCSS( elem, name, force );

src/dimensions.js

@@ -2,22 +2,21 @@
 jQuery.each([ "Height", "Width" ], function(i, name){
 
 	var tl = i ? "Left"  : "Top",  // top or left
-		br = i ? "Right" : "Bottom"; // bottom or right
+		br = i ? "Right" : "Bottom", // bottom or right
+		lower = name.toLowerCase();
 
 	// innerHeight and innerWidth
 	jQuery.fn["inner" + name] = function(){
-		return this[ name.toLowerCase() ]() +
-			num(this, "padding" + tl) +
-			num(this, "padding" + br);
+		return this[0] ?
+			jQuery.css( this[0], lower, false, "padding" ) :
+			null;
 	};
 
 	// outerHeight and outerWidth
 	jQuery.fn["outer" + name] = function(margin) {
-		return this["inner" + name]() +
-			num(this, "border" + tl + "Width") +
-			num(this, "border" + br + "Width") +
-			(margin ?
-				num(this, "margin" + tl) + num(this, "margin" + br) : 0);
+		return this[0] ?
+			jQuery.css( this[0], lower, false, margin ? "margin" : "border" ) :
+			null;
 	};
 
 	var type = name.toLowerCase();
@@ -47,4 +46,4 @@ jQuery.each([ "Height", "Width" ], function(i, name){
 					this.css( type, typeof size === "string" ? size : size + "px" );
 	};
 
-});
+});