CSS: Avoid filling jQuery.cssProps

Fixes gh-3986
Closes gh-4005

Avoids filling jQuery.cssProps by introducing a second internal
prop cache. This allows jQuery Migrate to detect external usage.

1 files changed, 39 insertions, 0 deletions

diff --git a/src/css/finalPropName.js b/src/css/finalPropName.js
new file mode 100644
index 000000000..e5c77b0b2
--- /dev/null
+++ b/src/css/finalPropName.js
@@ -0,0 +1,39 @@
+define( [ "../var/document" ], function( document ) {
+
+"use strict";
+
+var cssPrefixes = [ "Webkit", "Moz", "ms" ],
+	emptyStyle = document.createElement( "div" ).style,
+	vendorProps = {};
+
+// Return a vendor-prefixed property or undefined
+function vendorPropName( name ) {
+
+	// Check for vendor prefixed names
+	var capName = name[ 0 ].toUpperCase() + name.slice( 1 ),
+		i = cssPrefixes.length;
+
+	while ( i-- ) {
+		name = cssPrefixes[ i ] + capName;
+		if ( name in emptyStyle ) {
+			return name;
+		}
+	}
+}
+
+// Return a potentially-mapped jQuery.cssProps or vendor prefixed property
+function finalPropName( name ) {
+	var final = jQuery.cssProps[ name ] || vendorProps[ name ];
+
+	if ( final ) {
+		return final;
+	}
+	if ( name in emptyStyle ) {
+		return name;
+	}
+	return vendorProps[ name ] = vendorPropName( name ) || name;
+}
+
+return finalPropName;
+
+} );