I've recently stumbled across the following video by Damian Edwards of Microsoft. He gives a good intro to the intricacies of JavaScript, covering things like scope and closures before giving a great overview of JQuery. Definitely worth a watch.

If you are looking for a slightly more in-depth intro to jQuery then you could do a lot worse than sitting through Ray Camden's 'Introduction to jQuery' Udemy course which is a steal at only $20.