Ref #14313: NaN detection. Close gh-1352.

src/core.js

@@ -224,7 +224,10 @@ jQuery.extend({
 	},
 
 	isNumeric: function( obj ) {
-		return !isNaN( parseFloat(obj) ) && isFinite( obj );
+		// parseFloat NaNs numeric-cast false positives (null|true|false|"")
+		// ...but misinterprets leading-number strings, particularly hex literals ("0x...")
+		// subtraction forces infinities to NaN
+		return obj - parseFloat( obj ) >= 0;
 	},
 
 	isEmptyObject: function( obj ) {
@@ -426,7 +429,7 @@ jQuery.extend({
 		}
 
 		// Support: IE<9
-		// Workaround non-numeric length overrides of otherwise arraylike objects (e.g., NodeLists)
+		// Workaround casting of .length to NaN on otherwise arraylike objects (e.g., NodeLists)
 		if ( len !== len ) {
 			while ( second[j] !== undefined ) {
 				first[ i++ ] = second[ j++ ];

src/css.js

@@ -272,8 +272,8 @@ jQuery.extend({
 				type = "number";
 			}
 
-			// Make sure that NaN and null values aren't set. See: #7116
-			if ( value == null || type === "number" && isNaN( value ) ) {
+			// Make sure that null and NaN values aren't set. See: #7116
+			if ( value == null || value !== value ) {
 				return;
 			}