dojo.setObject
<html> <head> <script type="text/javascript"> var djConfig = { baseScriptUri : "js/dojo/" }; </script> <script type="text/javascript" src="js/dojo/dojo/dojo.js"></script> <script language="JavaScript" type="text/javascript"> dojo.setObject("person.names.firstName", "A"); alert(dojo.toJson(person)); </script> </head> <body></body> </html>