

I did the front-end program on freecodecamp.org a bunch of years ago, it was decent. The challenging part about finding what you’re looking for is that Javascript is used in both the front and back ends (and in a number of other places). Courses in JS will usually focus on backend (node.js is common), but it sounds like you’re looking for a basic front-end course.
Also note that “integrating front end with back end” is complicated and depends largely on the backend itself. In the free code camp course, I did some calls to APIs from the frontend, which I think is what you’re asking.
In any case, check out the Full Stack course on freecodecamp.org (specifically what you’re asking about is covered in the “DOM Manipulation and Events” section).
“Embedded control architect”