Also, as stated by John, JSlint will be used. That by itself avoid the big majority of JS' gotchas. And IMO, C++ has way more gotchas than Javascript and that doesn't stop universities to teach it as first language.

In fact, I think the first language is not just about giving a strong foundation but also give students the chance to find a good internship. So, with that logic, even though I enjoy hacking with Scheme, I'd feel bad to teach that to students who will try to find an internship and writing on their resumes "Scheme" while other universities students would have "C++/Java". And, please, before your argue that a language can be learned or something else, have in mind how companies recruit and parse resumes.. they often just search for a keyword. Now, one might say that you don't want to work for a company who does that, but then, you have to start somewhere in your first internship.

Thus, I like JavaScript as a first language; not because it's the easiest to learn but because I believe it gives a strong foundation but also gives students the ability to find a good internship.