What is the best practice for testing code to pinpoint a logic error within a script?

Zamar wants to add buttons to his Web page to allow users to navigate forward and backward through his Web site similar to the Forward and Back buttons in the Web browser window. Which JavaScript object will he use?

Consider the following code:

The JavaScript function above will display the following:

Juan is testing his JavaScript application, which includes the following code:

Assuming Juan enters August for his birth month and his name for first name, what is the value of birthMonth after executing this code?

Kirken needs to write a script to construct custom objects that store user account information such as a username. password and e-mail address for a Web site. What should he add to the following code to set these properties?

A)

B)

C)

D)