No manual.

Java, Python, Erlang and some other languages come with detailed documentation of the language and runtime which is sufficient to use the language. You are NOT at the mercy of StackOverflow and Google SEO Spammers if you want to answer simple questions.

In Javascript they blew up the tower of babel and dispersed the manual to the 4000 corners of a hypercube.

There are ways to compensate (MDN, the official ECMA docs punch above their readership weight, ...) and I have a feeling that the frenetic progress has slowed in the last two years but I dread teaching anybody else Javascript since I can't ground it in a epistemology the way I can with Python and Java.