How does jQuery protect overwriting jQuery and $

Question

These variables are located immediately after defining a local copy of jQuery in the jQuery source.

// Map over jQuery in case of overwrite
_jQuery = window         


        

Answer 1

If you were to include another library like prototype, which uses $, then jQuery needs to have a reference of both $ and window.jQuery in order to support the jQuery.noConflict() function, etc...

http://api.jquery.com/jQuery.noConflict/

$ is used because it is convenient, but this comes at the price that it may be used by more than one library.

Does that help?