JavaScript

Hi,
These are some of your options today as a JavaScript developer.
HTML, CSS, and JavaScript/JQuery: You can make stand alone websites or websites that connect to a back-end, which will be handled by a separate team. You might have to work on frameworks such as Bootstrap and Semantic UI (which make your job a lot easier once mastered).
Angular/ Backbone/ React/ Vue/ Ember: All of these are JavaScript frameworks/libraries for building single page, highly interactive websites. Consider these as an icing on top of everything mentioned in the previous point. All of these solve the same problem differently, and you will have to work with whatever suits your or your employers needs.
Node JS: Thanks to Node, you can also dive into the back end/server side programming without having programmed in any other language except JavaScript.
The MEAN/MERN stack: Pick an MV* framework from point 2, add Node from point 3, and throw in a database (Mongo DB in this case). There, you are now a full stack JavaScript developer. Okay, you are not, but you just added a lot of value to yourself.
Mobile/cross platform app development with Ionic/PhoneGap/React Native: All of these use JavaScript and other supporting technologies. Not many people take them seriously though.
There are also complete solutions like Meteor, which pretty much handle the back end for you, and let you focus on the UI. You can choose from Angular, Blaze, and React for the UI.
To sum it up, there are ton of opportunities right now, but that doesnt mean its going to be like this forever. If we were talking about something rock solid, like Java, I could rest easy knowing my job is secure, at least for a while. With the web, its a new, shiny thing everyday. We love jumping wagons.
All the best.