Make sure you are using the correct URL to retrieve the data. 
I just did a test of that example from the book by creating a controller and index view and it works as expected. 
In your original post you show
$.getJSON('/application/default/weekdays',
and in your last reply you suggest you tested it by viewing in browser
those are very different obviously but without further details I will assume you are using one or the other. 
/application needs to be the name of your actual application it could be "examples", "welcome", or some custom name you gave the application.