Fix #10466. jQuery.param() should treat object-wrapped primitives as primitives.

src/ajax.js

@@ -818,7 +818,7 @@ function buildParams( prefix, obj, traditional, add ) {
 			}
 		});
 
-	} else if ( !traditional && obj != null && typeof obj === "object" ) {
+	} else if ( !traditional && jQuery.isPlainObject( obj ) ) {
 		// Serialize object item.
 		for ( var name in obj ) {
 			buildParams( prefix + "[" + name + "]", obj[ name ], traditional, add );

test/unit/ajax.js

@@ -1031,6 +1031,19 @@ test("jQuery.param()", function() {
 	equal( jQuery.param( params, false ), "test%5Blength%5D=3&test%5Bfoo%5D=bar", "Sub-object with a length property" );
 });
 
+test("jQuery.param() Constructed prop values", function() {
+	expect(3);
+
+	var params = {"test": new String("foo") };
+	equal( jQuery.param( params, false ), "test=foo", "Do not mistake new String() for a plain object" );
+
+	params = {"test": new Number(5) };
+	equal( jQuery.param( params, false ), "test=5", "Do not mistake new Number() for a plain object" );
+
+	params = {"test": new Date() };
+	ok( jQuery.param( params, false ), "(Non empty string returned) Do not mistake new Date() for a plain object" );
+});
+
 test("synchronous request", function() {
 	expect(1);
 	ok( /^{ "data"/.test( jQuery.ajax({url: url("data/json_obj.js"), dataType: "text", async: false}).responseText ), "check returned text" );