In 1995, a Netscape employee wrote a hack in 10 days that now runs the Internet - Ars Technica

The 10-day creation story has become programming folklore, but even with that kernel of truth we mentioned, it tends to oversimplify the timeline. Eich’s sprint produced a working demo, not a finished language, and over the next year, Netscape continued tweaking the design. The rushed development left JavaScript with quirks and inconsistencies that developers still complain about today. So many changes were coming down the pipeline, in fact, that it began to annoy one of the industry’s most prominent figures at the time.