[jQuery] How to detect jQuery presence and include it on-the-fly?

[jQuery] How to detect jQuery presence and include it on-the-fly?


Greetings,
The task: include jQuery source on the fly in case it's not loaded.
The script is included on a third-party page and it's not possible to
guarantee the jQuery is already loaded.
What is the simplest way to do that?
Thanks!
All the best,
Konstantin