Mat Marquis (online as Wilto) is a US web developer and one of the long-running independent voices on responsive web design and the broader web-platform standards landscape. He is the chair of the Responsive Issues Community Group and the author of Responsible Responsive Design.
His CourseFlix listing carries JavaScript for Everyone — a comprehensive introduction to JavaScript aimed at the broad audience of web developers (including designers and content people) who want to add real JavaScript fluency to their craft.
Material is paid and aimed at web professionals across the design-and-development spectrum. For broader content, see CourseFlix's JavaScript category page.