I was a mainframe and java developer a few years back and I had a good interest in designing as well. Luckily I was in my masters degree and I happen to work with a small design firm. So when I started with them I directly started learning HTML and CSS with a live project. The designers here created the design in photoshop and my role is to make it working with HTML, CSS and JS. So take up a project or select some photoshop templates, try to code them using HTML,CSS and JS (master this). Once you code things in HTML, CSS and JS , using anything like angularjs, reactjs, JSP or whatever is just matter of understanding the file structures, templating and framework concepts.