For someone new to the field i.e. 1-2 years commercial experience. What is the employer expecting in terms of JS?
I feel I know HTML and CSS quite well and in the process of learning JS.
Another reinforcement… learn the basics of Javascript first - oodles upon oodles of tutorials and books exist to help you… then step into the plugins. The plugins end up being more or less abbreviations of the foundation scripts, so not knowing why the plugins exist may befuddle you. Start basic. Build up.
I’d suggest familiarizing yourself with the Prototype and jQuery libraries.
I suggest that you don’t do that until you know JavaScript to a reasonable level so that you know what can and can’t be done easily without the libraries.
I have seen large amounts of code people have written using those libraries that could be done in far fewer lines of ordinary JavaScript without the library. Since those libraries are written in JavaScript, you need a reasonable understanding of JavaScript in order to be able to use the libraries properly. Obviously these people are not web developers or they’d know how to use JavaScript properly.
Also a web developer can draw on their understanding of whatever server side languages they already know to pick up at least the basics of JavaScript reasonably quickly. A web designer with no programming experience would probably have more trouble with it but ideally they should be teamed up with a web developer who can take care of the programming side and leave them to just worry about the HTML and CSS - which should be their area of expertise in the way that web programming in JavaScript and server side languages is for the web developer.
I agree with Stephen. A good knowledge of the DOM and how normal JavaScript interacts with it is very useful when using jQuery. This is because there are things jQuery can’t do that require breaking out of its jQuery object system and actually using the DOM elements themselves.