Over the past 25 years, the Davidson College Physics Department has developed small computer programs called Physlets. These programs were written in Java and distributed as Java applets embedded in HTML pages. Physics teachers from around the world used Physlets to author interactive computer-based curricular materials for the teaching of introductory and advanced physics courses in multiple languages. Unfortunately, the Java plugin that enabled Java applets, including our original Physlets, to run was removed from browsers in 2018, Removing applet support, though critical for security reasons, was a major setback for physics education, since there had been thousands of applet-based HTML pages developed for physics and mathematics. To address this problem, we have converted Physlets to JavaScript so that they are compatible with all devices, inducing mobile platforms. This paper describes how these JavaScript Physlets can be used to improve teaching.