That being said, if you're applying for jobs you're qualified for, you should hit 50%, not 0%.
I wouldn't expect useful feedback from companies that interview you.
In your position I would look for a (paid) service that does a mock interview and gives you honest feedback. With minimum googling I found http://programminginterviewprep.com/. I'm sure there are others.
Alternatively, you can ask trusted people you know to do it for free, but then that might bias the feedback (people you know usually don't want to hurt your feelings; you need honest feedback).
Also, if people tell you that you don't enough experience in X (e.g. JavaScript) then it's most likely not "you've been doing it for 3.5 years and we really need 4" but "we want someone who knows JavaScript in-depth and based on our interview we don't believe you're on that level".
So to remedy that, fill your JavaScript gaps and go deep enough so that you can present yourself as know JavaScript in-depth.
Since perception > reality, you don't have to be 100% expert. Sometimes it's enough to do 1 in-deep investigation and then talk about that one thing (e.g. micro benchmark es6 construct vs. its es5 transpiled version in Chrome, write a blog post about it with methodology and nice graphs and try to inject that interview conversation).