In Chapter 3, Language Basics, Understanding Argument section, Page 82, it's mentioned that if any value in the arguments object is modified, it's also reflected in the named argument. But, if the value of the named argument is modified, the corresponding value is not changed in the arguments object.
However, this is not the case now as I've tested it on multiple browsers. The values in the named arguments and the arguments object are being kept in sync, no matter which one is modified. Can you let me if that's true or not.