I used to write (and probably still do, but to lesser extent) horrible Javascript. Nearly all older guides (anything older than a year) never focused on Javascript guidelines - and then I ended up watching Crockford videos.

My understanding of Javascript has increased; I now think of Javascript as a proper language to code in and not just a collection of statements to make HTML elements move/change-color. Crockford videos are a must see!

The only issue might be that there is a lot of repetition of concepts between videos and sometimes it gets boring, but it is always worth it.