There are some older global functions that are not in a namespace. Most of these start with a $ character. These are known as Non-namespace APIs.
Some functions return an interface, which is an object that contains functions known as methods and variables known as properties, that allows access to a specific instance of a page component or other entity.
TODO describe how to know which APIs are available when i.e. desktop vs mobile, core/default vs need to load a specific file.
When developing new applications, the legacy file is included by default in all applications that use a Desktop User Interface Type. New applications that use a jQuery Mobile Smartphone User Interface Type do not include this file.