MDN Web Docs focuses on the basics of HTML, CSS and JavaScript, among other aspects of web design, and has a learning pathway for aspiring front-end web developers.

In this course, students learn the fundamentals of design and gain experience with languages like CSS, HTML, JavaScript, React and Redux. Full-Stack Software Engineer Time to Completion: 6 months ...

The basic plan offered by Sololearn has free, short coding lessons in several computer languages; the pro plan includes interactive demos and other features for $70, billed annually.