If such things isn't available on the list, then most likely it's not. It's good to see you built without external library.
On a side note, i think ";" at the beginning of code (after usercript) isn't needed.
I don't know JQuery and don't use it, because I've started learning JS around 1.5 years ago, and at that point standard library was so good that you don't need any libraries for basic DOM manipulation.
The ";" was inserted by my linter, it's still valid Javascript, so I didn't bother to remove it. It can help if someone will copypaste this code into a bigger userscript, for example.