Auth0 have a neat playground where you can play around with the Lock settings.
Lock is the Auth0 login component.
I was trying to get some extra fields added when the user wants to self-register and we want to capture some extra information.
There are examples but they don't have context i.e. they show you what attribute to set but you don't get to see the full picture.
As usual, the gist is here.
This is the basic screen - notice I've added some of the Asian social providers like Baidu. This isn't part of the js - it's part of the application configuration.
Here is the signup screen. Clicking "United States" shows the drop-down. Also notice the checkbox at the bottom.
Shortening the text shows the error message that is part of the validation.