The next steps depend on what you want to do. The most popular way to further learn JavaScript is to learn web development tools.
It is important to users that pages in an online store, social networking site or news portal load quickly, and in turn it is important to owners that users do not leave their sites because of a slow interface. It was in the pursuit of speed and performance that JavaScript frameworks such as Angular, Vue.js, and the React library came into being.
With their help, developers were able to move from Server Side Rendering to Client Side Rendering, that is, in the browser. As part of this transition, the concept of Single Page Application emerged.
Such applications only load the markup from the server once, and then, when switching to new pages, the information requested from the server comes in a special format, without HTML tags. This works much faster than transferring each requested page from the server to the browser.
You should start learning frameworks with Vue.js. It’s based on the same concepts as React and Angular, but it’s later, better organized, and more logical, so it’s easier for beginners to understand. There is also detailed documentation for Vue.