The web is full of great places to learn more about JavaScript and jQuery. Here are some sites I recommend (and some notes on why I don't recommend others.)
If you Google an issue you are having with JavaScript, you are bound to see links to the site W3 Schools (w3schools.com). The name makes it sound like the site is affiliated with the W3C, the parent organization for the web. However, there is no relationship at all. I've found outdated and incorrect information on w3schools sites, so I recommend you avoid it. Look on Stack Exchange instead to get details about JavaScript methods or properties.