Check if another script is loaded without using JQUERY

Check if another script is loaded without using JQUERY

I have two different that are somewhat depending on eachother (i.e one of
the script has a function that calls the other script)
Now i wont go into any details other than saying i am not able to load one
before the other.
Because of this i need to make a check in the scripts to check if the
other script is loaded (So that the scripts "waits" for eachother).
My Boss does NOT want me to use Jquery so i was wondering is there a way
in Plain javascript to check if another script is loaded? And if so how?